diff --git a/src/autocomplete/UserProvider.tsx b/src/autocomplete/UserProvider.tsx
index 22bd307b47..3d4c542c48 100644
--- a/src/autocomplete/UserProvider.tsx
+++ b/src/autocomplete/UserProvider.tsx
@@ -74,7 +74,7 @@ export default class UserProvider extends AutocompleteProvider {
     private onRoomTimeline = (
         ev: MatrixEvent,
         room: Room | undefined,
-        toStartOfTimeline: boolean,
+        toStartOfTimeline: boolean | undefined,
         removed: boolean,
         data: IRoomTimelineData,
     ): void => {
diff --git a/src/components/structures/FilePanel.tsx b/src/components/structures/FilePanel.tsx
index ab7dd8ba5d..49c7dfebae 100644
--- a/src/components/structures/FilePanel.tsx
+++ b/src/components/structures/FilePanel.tsx
@@ -67,7 +67,7 @@ class FilePanel extends React.Component<IProps, IState> {
     private onRoomTimeline = (
         ev: MatrixEvent,
         room: Room | undefined,
-        toStartOfTimeline: boolean,
+        toStartOfTimeline: boolean | undefined,
         removed: boolean,
         data: IRoomTimelineData,
     ): void => {
diff --git a/src/components/structures/MatrixChat.tsx b/src/components/structures/MatrixChat.tsx
index 9932a102ef..4aea34870c 100644
--- a/src/components/structures/MatrixChat.tsx
+++ b/src/components/structures/MatrixChat.tsx
@@ -113,7 +113,7 @@ import { PosthogAnalytics } from "../../PosthogAnalytics";
 import { initSentry } from "../../sentry";
 import LegacyCallHandler from "../../LegacyCallHandler";
 import { showSpaceInvite } from "../../utils/space";
-import AccessibleButton from "../views/elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../views/elements/AccessibleButton";
 import { ActionPayload } from "../../dispatcher/payloads";
 import { SummarizedNotificationState } from "../../stores/notifications/SummarizedNotificationState";
 import Views from "../../Views";
@@ -1874,7 +1874,7 @@ export default class MatrixChat extends React.PureComponent<IProps, IState> {
         this.setPageSubtitle();
     }
 
-    private onLogoutClick(event: React.MouseEvent<HTMLAnchorElement, MouseEvent>): void {
+    private onLogoutClick(event: ButtonEvent): void {
         dis.dispatch({
             action: "logout",
         });
diff --git a/src/components/structures/RoomView.tsx b/src/components/structures/RoomView.tsx
index c11892d22c..b4a38ee2eb 100644
--- a/src/components/structures/RoomView.tsx
+++ b/src/components/structures/RoomView.tsx
@@ -1461,7 +1461,7 @@ export class RoomView extends React.Component<IRoomProps, IRoomState> {
         this.updateRoomMembers();
     };
 
-    private onMyMembership = (room: Room, membership: string, oldMembership: string): void => {
+    private onMyMembership = (room: Room): void => {
         if (room.roomId === this.state.roomId) {
             this.forceUpdate();
             this.loadMembersIfJoined(room);
diff --git a/src/components/structures/TimelinePanel.tsx b/src/components/structures/TimelinePanel.tsx
index 874d0b7a34..75f8fe0d4f 100644
--- a/src/components/structures/TimelinePanel.tsx
+++ b/src/components/structures/TimelinePanel.tsx
@@ -666,7 +666,7 @@ class TimelinePanel extends React.Component<IProps, IState> {
     private onRoomTimeline = (
         ev: MatrixEvent,
         room: Room | undefined,
-        toStartOfTimeline: boolean,
+        toStartOfTimeline: boolean | undefined,
         removed: boolean,
         data: IRoomTimelineData,
     ): void => {
@@ -769,7 +769,7 @@ class TimelinePanel extends React.Component<IProps, IState> {
             });
     };
 
-    private onRoomTimelineReset = (room: Room, timelineSet: EventTimelineSet): void => {
+    private onRoomTimelineReset = (room: Room | undefined, timelineSet: EventTimelineSet): void => {
         if (timelineSet !== this.props.timelineSet) return;
 
         if (this.canResetTimeline()) {
@@ -873,7 +873,7 @@ class TimelinePanel extends React.Component<IProps, IState> {
         this.forceUpdate();
     };
 
-    private onLocalEchoUpdated = (ev: MatrixEvent, room: Room, oldEventId: string): void => {
+    private onLocalEchoUpdated = (ev: MatrixEvent, room: Room, oldEventId?: string): void => {
         if (this.unmounted) return;
 
         // ignore events for other rooms
@@ -921,7 +921,7 @@ class TimelinePanel extends React.Component<IProps, IState> {
         this.forceUpdate();
     };
 
-    private onSync = (clientSyncState: SyncState, prevState: SyncState, data: object): void => {
+    private onSync = (clientSyncState: SyncState, prevState: SyncState | null, data?: object): void => {
         if (this.unmounted) return;
         this.setState({ clientSyncState });
     };
diff --git a/src/components/structures/UserMenu.tsx b/src/components/structures/UserMenu.tsx
index 609bcdf3e4..8a2d08f6cc 100644
--- a/src/components/structures/UserMenu.tsx
+++ b/src/components/structures/UserMenu.tsx
@@ -113,7 +113,7 @@ export default class UserMenu extends React.Component<IProps, IState> {
         return !!getHomePageUrl(SdkConfig.get());
     }
 
-    private onCurrentVoiceBroadcastRecordingChanged = (recording: VoiceBroadcastRecording): void => {
+    private onCurrentVoiceBroadcastRecordingChanged = (recording: VoiceBroadcastRecording | null): void => {
         this.setState({
             showLiveAvatarAddon: recording !== null,
         });
@@ -195,7 +195,7 @@ export default class UserMenu extends React.Component<IProps, IState> {
         }
     };
 
-    private onOpenMenuClick = (ev: React.MouseEvent): void => {
+    private onOpenMenuClick = (ev: ButtonEvent): void => {
         ev.preventDefault();
         ev.stopPropagation();
         this.setState({ contextMenuPosition: ev.currentTarget.getBoundingClientRect() });
@@ -218,7 +218,7 @@ export default class UserMenu extends React.Component<IProps, IState> {
         this.setState({ contextMenuPosition: null });
     };
 
-    private onSwitchThemeClick = (ev: React.MouseEvent): void => {
+    private onSwitchThemeClick = (ev: ButtonEvent): void => {
         ev.preventDefault();
         ev.stopPropagation();
 
diff --git a/src/components/structures/auth/SetupEncryptionBody.tsx b/src/components/structures/auth/SetupEncryptionBody.tsx
index 2cbfbf8367..d94718ab60 100644
--- a/src/components/structures/auth/SetupEncryptionBody.tsx
+++ b/src/components/structures/auth/SetupEncryptionBody.tsx
@@ -26,7 +26,7 @@ import Modal from "../../../Modal";
 import VerificationRequestDialog from "../../views/dialogs/VerificationRequestDialog";
 import { SetupEncryptionStore, Phase } from "../../../stores/SetupEncryptionStore";
 import EncryptionPanel from "../../views/right_panel/EncryptionPanel";
-import AccessibleButton from "../../views/elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../../views/elements/AccessibleButton";
 import Spinner from "../../views/elements/Spinner";
 
 function keyHasPassphrase(keyInfo: ISecretStorageKeyInfo): boolean {
@@ -115,7 +115,7 @@ export default class SetupEncryptionBody extends React.Component<IProps, IState>
         store.returnAfterSkip();
     };
 
-    private onResetClick = (ev: React.MouseEvent<HTMLButtonElement>): void => {
+    private onResetClick = (ev: ButtonEvent): void => {
         ev.preventDefault();
         const store = SetupEncryptionStore.sharedInstance();
         store.reset();
diff --git a/src/components/views/auth/InteractiveAuthEntryComponents.tsx b/src/components/views/auth/InteractiveAuthEntryComponents.tsx
index 8431bfc01c..cefdecab5e 100644
--- a/src/components/views/auth/InteractiveAuthEntryComponents.tsx
+++ b/src/components/views/auth/InteractiveAuthEntryComponents.tsx
@@ -18,14 +18,14 @@ import classNames from "classnames";
 import { MatrixClient } from "matrix-js-sdk/src/client";
 import { AuthType, IAuthDict, IInputs, IStageStatus } from "matrix-js-sdk/src/interactive-auth";
 import { logger } from "matrix-js-sdk/src/logger";
-import React, { ChangeEvent, createRef, FormEvent, Fragment, MouseEvent } from "react";
+import React, { ChangeEvent, createRef, FormEvent, Fragment } from "react";
 
 import EmailPromptIcon from "../../../../res/img/element-icons/email-prompt.svg";
 import { _t } from "../../../languageHandler";
 import SettingsStore from "../../../settings/SettingsStore";
 import { LocalisedPolicy, Policies } from "../../../Terms";
 import { AuthHeaderModifier } from "../../structures/auth/header/AuthHeaderModifier";
-import AccessibleButton from "../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../elements/AccessibleButton";
 import AccessibleTooltipButton from "../elements/AccessibleTooltipButton";
 import Field from "../elements/Field";
 import Spinner from "../elements/Spinner";
@@ -943,7 +943,7 @@ export class FallbackAuthEntry extends React.Component<IAuthEntryProps> {
         this.fallbackButton.current?.focus();
     };
 
-    private onShowFallbackClick = (e: MouseEvent): void => {
+    private onShowFallbackClick = (e: ButtonEvent): void => {
         if (!this.props.authSessionId) return;
 
         e.preventDefault();
diff --git a/src/components/views/avatars/BaseAvatar.tsx b/src/components/views/avatars/BaseAvatar.tsx
index 5e9356d09e..277eb673e8 100644
--- a/src/components/views/avatars/BaseAvatar.tsx
+++ b/src/components/views/avatars/BaseAvatar.tsx
@@ -24,7 +24,7 @@ import { ClientEvent } from "matrix-js-sdk/src/client";
 
 import * as AvatarLogic from "../../../Avatar";
 import SettingsStore from "../../../settings/SettingsStore";
-import AccessibleButton from "../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../elements/AccessibleButton";
 import RoomContext from "../../../contexts/RoomContext";
 import MatrixClientContext from "../../../contexts/MatrixClientContext";
 import { useTypedEventEmitter } from "../../../hooks/useEventEmitter";
@@ -42,7 +42,7 @@ interface IProps {
     // XXX: resizeMethod not actually used.
     resizeMethod?: ResizeMethod;
     defaultToInitialLetter?: boolean; // true to add default url
-    onClick?: React.MouseEventHandler;
+    onClick?: (ev: ButtonEvent) => void;
     inputRef?: React.RefObject<HTMLImageElement & HTMLSpanElement>;
     className?: string;
     tabIndex?: number;
diff --git a/src/components/views/avatars/MemberAvatar.tsx b/src/components/views/avatars/MemberAvatar.tsx
index a17f18926c..c1a19261e2 100644
--- a/src/components/views/avatars/MemberAvatar.tsx
+++ b/src/components/views/avatars/MemberAvatar.tsx
@@ -33,8 +33,6 @@ interface IProps extends Omit<React.ComponentProps<typeof BaseAvatar>, "name" |
     width: number;
     height: number;
     resizeMethod?: ResizeMethod;
-    // The onClick to give the avatar
-    onClick?: React.MouseEventHandler;
     // Whether the onClick of the avatar should be overridden to dispatch `Action.ViewUser`
     viewUserOnClick?: boolean;
     pushUserOnClick?: boolean;
diff --git a/src/components/views/dialogs/StorageEvictedDialog.tsx b/src/components/views/dialogs/StorageEvictedDialog.tsx
index df27c4a31d..9c81b0192c 100644
--- a/src/components/views/dialogs/StorageEvictedDialog.tsx
+++ b/src/components/views/dialogs/StorageEvictedDialog.tsx
@@ -22,14 +22,14 @@ import { _t } from "../../../languageHandler";
 import BaseDialog from "./BaseDialog";
 import DialogButtons from "../elements/DialogButtons";
 import BugReportDialog from "./BugReportDialog";
-import AccessibleButton from "../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../elements/AccessibleButton";
 
 interface IProps {
     onFinished(signOut?: boolean): void;
 }
 
 export default class StorageEvictedDialog extends React.Component<IProps> {
-    private sendBugReport = (ev: React.MouseEvent): void => {
+    private sendBugReport = (ev: ButtonEvent): void => {
         ev.preventDefault();
         Modal.createDialog(BugReportDialog, {});
     };
diff --git a/src/components/views/dialogs/security/AccessSecretStorageDialog.tsx b/src/components/views/dialogs/security/AccessSecretStorageDialog.tsx
index 9cffc20241..682445833e 100644
--- a/src/components/views/dialogs/security/AccessSecretStorageDialog.tsx
+++ b/src/components/views/dialogs/security/AccessSecretStorageDialog.tsx
@@ -22,7 +22,7 @@ import { logger } from "matrix-js-sdk/src/logger";
 
 import { MatrixClientPeg } from "../../../../MatrixClientPeg";
 import Field from "../../elements/Field";
-import AccessibleButton from "../../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../../elements/AccessibleButton";
 import { _t } from "../../../../languageHandler";
 import { accessSecretStorage } from "../../../../SecurityManager";
 import Modal from "../../../../Modal";
@@ -217,7 +217,7 @@ export default class AccessSecretStorageDialog extends React.PureComponent<IProp
         });
     };
 
-    private onResetAllClick = (ev: React.MouseEvent<HTMLAnchorElement>): void => {
+    private onResetAllClick = (ev: ButtonEvent): void => {
         ev.preventDefault();
         this.setState({ resetting: true });
     };
diff --git a/src/components/views/elements/AppTile.tsx b/src/components/views/elements/AppTile.tsx
index 1fa1fba752..a90e01f317 100644
--- a/src/components/views/elements/AppTile.tsx
+++ b/src/components/views/elements/AppTile.tsx
@@ -106,7 +106,7 @@ interface IState {
 
 export default class AppTile extends React.Component<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context: ContextType<typeof MatrixClientContext>;
+    public context!: ContextType<typeof MatrixClientContext>;
 
     public static defaultProps: Partial<IProps> = {
         waitForIframeLoad: true,
diff --git a/src/components/views/elements/PersistentApp.tsx b/src/components/views/elements/PersistentApp.tsx
index a13588b96b..d6ed5d6bf8 100644
--- a/src/components/views/elements/PersistentApp.tsx
+++ b/src/components/views/elements/PersistentApp.tsx
@@ -32,7 +32,7 @@ interface IProps {
 
 export default class PersistentApp extends React.Component<IProps> {
     public static contextType = MatrixClientContext;
-    public context: ContextType<typeof MatrixClientContext>;
+    public context!: ContextType<typeof MatrixClientContext>;
     private room: Room;
 
     public constructor(props: IProps, context: ContextType<typeof MatrixClientContext>) {
diff --git a/src/components/views/messages/MBeaconBody.tsx b/src/components/views/messages/MBeaconBody.tsx
index 25327df74e..20cfaf1411 100644
--- a/src/components/views/messages/MBeaconBody.tsx
+++ b/src/components/views/messages/MBeaconBody.tsx
@@ -131,7 +131,7 @@ const useHandleBeaconRedaction = (
     }, [event, onBeforeBeaconInfoRedaction]);
 };
 
-const MBeaconBody: React.FC<IBodyProps> = React.forwardRef(({ mxEvent, getRelationsForEvent }, ref) => {
+const MBeaconBody = React.forwardRef<HTMLDivElement, IBodyProps>(({ mxEvent, getRelationsForEvent }, ref) => {
     const { beacon, isLive, latestLocationState, waitingToStart } = useBeaconState(mxEvent);
     const mapId = useUniqueId(mxEvent.getId()!);
 
diff --git a/src/components/views/messages/MessageActionBar.tsx b/src/components/views/messages/MessageActionBar.tsx
index 78d001ae95..f94bdf5f16 100644
--- a/src/components/views/messages/MessageActionBar.tsx
+++ b/src/components/views/messages/MessageActionBar.tsx
@@ -58,6 +58,7 @@ import { ShowThreadPayload } from "../../../dispatcher/payloads/ShowThreadPayloa
 import useFavouriteMessages from "../../../hooks/useFavouriteMessages";
 import { GetRelationsForEvent } from "../rooms/EventTile";
 import { VoiceBroadcastInfoEventType } from "../../../voice-broadcast/types";
+import { ButtonEvent } from "../elements/AccessibleButton";
 
 interface IOptionsButtonProps {
     mxEvent: MatrixEvent;
@@ -84,7 +85,7 @@ const OptionsButton: React.FC<IOptionsButtonProps> = ({
     }, [onFocusChange, menuDisplayed]);
 
     const onOptionsClick = useCallback(
-        (e: React.MouseEvent): void => {
+        (e: ButtonEvent): void => {
             // Don't open the regular browser or our context menu on right-click
             e.preventDefault();
             e.stopPropagation();
@@ -159,7 +160,7 @@ const ReactButton: React.FC<IReactButtonProps> = ({ mxEvent, reactions, onFocusC
     }
 
     const onClick = useCallback(
-        (e: React.MouseEvent) => {
+        (e: ButtonEvent) => {
             // Don't open the regular browser or our context menu on right-click
             e.preventDefault();
             e.stopPropagation();
@@ -203,7 +204,7 @@ const ReplyInThreadButton: React.FC<IReplyInThreadButton> = ({ mxEvent }) => {
     const relationType = mxEvent?.getRelation()?.rel_type;
     const hasARelation = !!relationType && relationType !== RelationType.Thread;
 
-    const onClick = (e: React.MouseEvent): void => {
+    const onClick = (e: ButtonEvent): void => {
         // Don't open the regular browser or our context menu on right-click
         e.preventDefault();
         e.stopPropagation();
@@ -266,7 +267,7 @@ const FavouriteButton: React.FC<IFavouriteButtonProp> = ({ mxEvent }) => {
     });
 
     const onClick = useCallback(
-        (e: React.MouseEvent) => {
+        (e: ButtonEvent) => {
             // Don't open the regular browser or our context menu on right-click
             e.preventDefault();
             e.stopPropagation();
@@ -345,7 +346,7 @@ export default class MessageActionBar extends React.PureComponent<IMessageAction
         this.props.onFocusChange?.(focused);
     };
 
-    private onReplyClick = (e: React.MouseEvent): void => {
+    private onReplyClick = (e: ButtonEvent): void => {
         // Don't open the regular browser or our context menu on right-click
         e.preventDefault();
         e.stopPropagation();
@@ -357,7 +358,7 @@ export default class MessageActionBar extends React.PureComponent<IMessageAction
         });
     };
 
-    private onEditClick = (e: React.MouseEvent): void => {
+    private onEditClick = (e: ButtonEvent): void => {
         // Don't open the regular browser or our context menu on right-click
         e.preventDefault();
         e.stopPropagation();
@@ -406,7 +407,7 @@ export default class MessageActionBar extends React.PureComponent<IMessageAction
         }
     }
 
-    private onResendClick = (ev: React.MouseEvent): void => {
+    private onResendClick = (ev: ButtonEvent): void => {
         // Don't open the regular browser or our context menu on right-click
         ev.preventDefault();
         ev.stopPropagation();
@@ -414,7 +415,7 @@ export default class MessageActionBar extends React.PureComponent<IMessageAction
         this.runActionOnFailedEv((tarEv) => Resend.resend(tarEv));
     };
 
-    private onCancelClick = (ev: React.MouseEvent): void => {
+    private onCancelClick = (ev: ButtonEvent): void => {
         this.runActionOnFailedEv(
             (tarEv) => Resend.removeFromQueue(tarEv),
             (testEv) => canCancel(testEv.status),
diff --git a/src/components/views/messages/UnknownBody.tsx b/src/components/views/messages/UnknownBody.tsx
index 419ec5971e..ec32449e92 100644
--- a/src/components/views/messages/UnknownBody.tsx
+++ b/src/components/views/messages/UnknownBody.tsx
@@ -23,7 +23,7 @@ interface IProps {
     children?: React.ReactNode;
 }
 
-export default forwardRef(({ mxEvent, children }: IProps, ref: React.RefObject<HTMLDivElement>) => {
+export default forwardRef<HTMLDivElement, IProps>(({ mxEvent, children }, ref) => {
     const text = mxEvent.getContent().body;
     return (
         <div className="mx_UnknownBody" ref={ref}>
diff --git a/src/components/views/messages/ViewSourceEvent.tsx b/src/components/views/messages/ViewSourceEvent.tsx
index 344ddd344e..1d33074a7a 100644
--- a/src/components/views/messages/ViewSourceEvent.tsx
+++ b/src/components/views/messages/ViewSourceEvent.tsx
@@ -20,7 +20,7 @@ import classNames from "classnames";
 
 import { MatrixClientPeg } from "../../../MatrixClientPeg";
 import { _t } from "../../../languageHandler";
-import AccessibleButton from "../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../elements/AccessibleButton";
 
 interface IProps {
     mxEvent: MatrixEvent;
@@ -50,7 +50,7 @@ export default class ViewSourceEvent extends React.PureComponent<IProps, IState>
         }
     }
 
-    private onToggle = (ev: React.MouseEvent): void => {
+    private onToggle = (ev: ButtonEvent): void => {
         ev.preventDefault();
         const { expanded } = this.state;
         this.setState({
diff --git a/src/components/views/room_settings/AliasSettings.tsx b/src/components/views/room_settings/AliasSettings.tsx
index f6a6f32e4f..ab92feca76 100644
--- a/src/components/views/room_settings/AliasSettings.tsx
+++ b/src/components/views/room_settings/AliasSettings.tsx
@@ -102,7 +102,7 @@ interface IState {
 
 export default class AliasSettings extends React.Component<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context: ContextType<typeof MatrixClientContext>;
+    public context!: ContextType<typeof MatrixClientContext>;
 
     public static defaultProps = {
         canSetAliases: false,
diff --git a/src/components/views/room_settings/RoomProfileSettings.tsx b/src/components/views/room_settings/RoomProfileSettings.tsx
index 573a1f6933..7117608f39 100644
--- a/src/components/views/room_settings/RoomProfileSettings.tsx
+++ b/src/components/views/room_settings/RoomProfileSettings.tsx
@@ -22,7 +22,7 @@ import { _t } from "../../../languageHandler";
 import { MatrixClientPeg } from "../../../MatrixClientPeg";
 import Field from "../elements/Field";
 import { mediaFromMxc } from "../../../customisations/Media";
-import AccessibleButton from "../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../elements/AccessibleButton";
 import AvatarSetting from "../settings/AvatarSetting";
 import { htmlSerializeFromMdIfNeeded } from "../../../editor/serialize";
 import { chromeFileInputFix } from "../../../utils/BrowserWorkarounds";
@@ -103,7 +103,7 @@ export default class RoomProfileSettings extends React.Component<IProps, IState>
         return Boolean(Object.values(this.state.profileFieldsTouched).length);
     };
 
-    private cancelProfileChanges = async (e: React.MouseEvent): Promise<void> => {
+    private cancelProfileChanges = async (e: ButtonEvent): Promise<void> => {
         e.stopPropagation();
         e.preventDefault();
 
diff --git a/src/components/views/rooms/EventTile.tsx b/src/components/views/rooms/EventTile.tsx
index 13a8e6b006..07015fee72 100644
--- a/src/components/views/rooms/EventTile.tsx
+++ b/src/components/views/rooms/EventTile.tsx
@@ -15,7 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { createRef, forwardRef, MouseEvent, ReactNode, RefObject, useRef } from "react";
+import React, { createRef, forwardRef, MouseEvent, ReactNode, useRef } from "react";
 import classNames from "classnames";
 import { EventType, MsgType, RelationType } from "matrix-js-sdk/src/@types/event";
 import { EventStatus, MatrixEvent, MatrixEventEvent } from "matrix-js-sdk/src/models/event";
@@ -1437,7 +1437,7 @@ export class UnwrappedEventTile extends React.Component<EventTileProps, IState>
 }
 
 // Wrap all event tiles with the tile error boundary so that any throws even during construction are captured
-const SafeEventTile = forwardRef((props: EventTileProps, ref: RefObject<UnwrappedEventTile>) => {
+const SafeEventTile = forwardRef<UnwrappedEventTile, EventTileProps>((props, ref) => {
     return (
         <>
             <TileErrorBoundary mxEvent={props.mxEvent} layout={props.layout ?? Layout.Group}>
diff --git a/src/components/views/rooms/JumpToBottomButton.tsx b/src/components/views/rooms/JumpToBottomButton.tsx
index a732d2cc32..bbff1d9605 100644
--- a/src/components/views/rooms/JumpToBottomButton.tsx
+++ b/src/components/views/rooms/JumpToBottomButton.tsx
@@ -18,12 +18,12 @@ import React from "react";
 import classNames from "classnames";
 
 import { _t } from "../../../languageHandler";
-import AccessibleButton from "../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../elements/AccessibleButton";
 
 interface IProps {
     numUnreadMessages?: number;
     highlight: boolean;
-    onScrollToBottomClick: (e: React.MouseEvent) => void;
+    onScrollToBottomClick: (e: ButtonEvent) => void;
 }
 
 const JumpToBottomButton: React.FC<IProps> = (props) => {
diff --git a/src/components/views/rooms/MemberList.tsx b/src/components/views/rooms/MemberList.tsx
index 44dba2e32b..bcc4c4fb97 100644
--- a/src/components/views/rooms/MemberList.tsx
+++ b/src/components/views/rooms/MemberList.tsx
@@ -142,7 +142,7 @@ export default class MemberList extends React.Component<IProps, IState> {
         };
     }
 
-    private onUserPresenceChange = (event: MatrixEvent, user: User): void => {
+    private onUserPresenceChange = (event: MatrixEvent | undefined, user: User): void => {
         // Attach a SINGLE listener for global presence changes then locate the
         // member tile and re-render it. This is more efficient than every tile
         // ever attaching their own listener.
@@ -162,7 +162,7 @@ export default class MemberList extends React.Component<IProps, IState> {
         this.updateListNow(true);
     };
 
-    private onMyMembership = (room: Room, membership: string, oldMembership: string): void => {
+    private onMyMembership = (room: Room, membership: string, oldMembership?: string): void => {
         if (room.roomId === this.props.roomId && membership === "join" && oldMembership !== "join") {
             // we just joined the room, load the member list
             this.updateListNow(true);
diff --git a/src/components/views/rooms/MessageComposerButtons.tsx b/src/components/views/rooms/MessageComposerButtons.tsx
index 81491d35c2..bfd9906e7e 100644
--- a/src/components/views/rooms/MessageComposerButtons.tsx
+++ b/src/components/views/rooms/MessageComposerButtons.tsx
@@ -17,7 +17,7 @@ limitations under the License.
 import classNames from "classnames";
 import { IEventRelation } from "matrix-js-sdk/src/models/event";
 import { M_POLL_START } from "matrix-js-sdk/src/@types/polls";
-import React, { createContext, MouseEventHandler, ReactElement, ReactNode, useContext, useRef } from "react";
+import React, { createContext, ReactElement, ReactNode, useContext, useRef } from "react";
 import { Room } from "matrix-js-sdk/src/models/room";
 import { MatrixClient } from "matrix-js-sdk/src/client";
 import { THREAD_RELATION_TYPE } from "matrix-js-sdk/src/models/thread";
@@ -40,6 +40,7 @@ import { chromeFileInputFix } from "../../../utils/BrowserWorkarounds";
 import IconizedContextMenu, { IconizedContextMenuOptionList } from "../context_menus/IconizedContextMenu";
 import { EmojiButton } from "./EmojiButton";
 import { useSettingValue } from "../../../hooks/useSettings";
+import { ButtonEvent } from "../elements/AccessibleButton";
 
 interface IProps {
     addEmoji: (emoji: string) => boolean;
@@ -362,7 +363,7 @@ function showLocationButton(props: IProps, room: Room, matrixClient: MatrixClien
 
 interface WysiwygToggleButtonProps {
     isRichTextEnabled: boolean;
-    onClick: MouseEventHandler<HTMLDivElement>;
+    onClick: (ev: ButtonEvent) => void;
 }
 
 function ComposerModeButton({ isRichTextEnabled, onClick }: WysiwygToggleButtonProps): JSX.Element {
diff --git a/src/components/views/rooms/NotificationBadge/StatelessNotificationBadge.tsx b/src/components/views/rooms/NotificationBadge/StatelessNotificationBadge.tsx
index d6083507f0..1055ee07b2 100644
--- a/src/components/views/rooms/NotificationBadge/StatelessNotificationBadge.tsx
+++ b/src/components/views/rooms/NotificationBadge/StatelessNotificationBadge.tsx
@@ -18,7 +18,7 @@ import React, { MouseEvent, ReactNode } from "react";
 import classNames from "classnames";
 
 import { formatCount } from "../../../../utils/FormattingUtils";
-import AccessibleButton from "../../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../../elements/AccessibleButton";
 import { NotificationColor } from "../../../../stores/notifications/NotificationColor";
 import { useSettingValue } from "../../../../hooks/useSettings";
 import { XOR } from "../../../../@types/common";
@@ -37,7 +37,7 @@ interface ClickableProps extends Props {
     /**
      * If specified will return an AccessibleButton instead of a div.
      */
-    onClick(ev: React.MouseEvent): void;
+    onClick(ev: ButtonEvent): void;
     tabIndex?: number;
 }
 
diff --git a/src/components/views/rooms/RoomSublist.tsx b/src/components/views/rooms/RoomSublist.tsx
index c4b3efa3e6..ccb3c77f8e 100644
--- a/src/components/views/rooms/RoomSublist.tsx
+++ b/src/components/views/rooms/RoomSublist.tsx
@@ -48,7 +48,7 @@ import ContextMenu, {
     StyledMenuItemCheckbox,
     StyledMenuItemRadio,
 } from "../../structures/ContextMenu";
-import AccessibleButton from "../../views/elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../../views/elements/AccessibleButton";
 import AccessibleTooltipButton from "../elements/AccessibleTooltipButton";
 import ExtraTile from "./ExtraTile";
 import SettingsStore from "../../../settings/SettingsStore";
@@ -369,7 +369,7 @@ export default class RoomSublist extends React.Component<IProps, IState> {
         }
     };
 
-    private onOpenMenuClick = (ev: React.MouseEvent): void => {
+    private onOpenMenuClick = (ev: ButtonEvent): void => {
         ev.preventDefault();
         ev.stopPropagation();
         const target = ev.target as HTMLButtonElement;
diff --git a/src/components/views/rooms/RoomTile.tsx b/src/components/views/rooms/RoomTile.tsx
index 58664951df..a5abb16a8f 100644
--- a/src/components/views/rooms/RoomTile.tsx
+++ b/src/components/views/rooms/RoomTile.tsx
@@ -220,11 +220,11 @@ export class RoomTile extends React.PureComponent<ClassProps, State> {
         });
     };
 
-    private onTileClick = async (ev: React.KeyboardEvent): Promise<void> => {
+    private onTileClick = async (ev: ButtonEvent): Promise<void> => {
         ev.preventDefault();
         ev.stopPropagation();
 
-        const action = getKeyBindingsManager().getAccessibilityAction(ev);
+        const action = getKeyBindingsManager().getAccessibilityAction(ev as React.KeyboardEvent);
         const clearSearch = ([KeyBindingAction.Enter, KeyBindingAction.Space] as Array<string | undefined>).includes(
             action,
         );
diff --git a/src/components/views/rooms/TopUnreadMessagesBar.tsx b/src/components/views/rooms/TopUnreadMessagesBar.tsx
index 51e67e611b..ffead7d53a 100644
--- a/src/components/views/rooms/TopUnreadMessagesBar.tsx
+++ b/src/components/views/rooms/TopUnreadMessagesBar.tsx
@@ -17,11 +17,11 @@ limitations under the License.
 import React from "react";
 
 import { _t } from "../../../languageHandler";
-import AccessibleButton from "../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../elements/AccessibleButton";
 
 interface IProps {
-    onScrollUpClick: (e: React.MouseEvent) => void;
-    onCloseClick: (e: React.MouseEvent) => void;
+    onScrollUpClick: (e: ButtonEvent) => void;
+    onCloseClick: (e: ButtonEvent) => void;
 }
 
 export default class TopUnreadMessagesBar extends React.PureComponent<IProps> {
diff --git a/src/components/views/settings/ProfileSettings.tsx b/src/components/views/settings/ProfileSettings.tsx
index d8ef992835..8f962ba38e 100644
--- a/src/components/views/settings/ProfileSettings.tsx
+++ b/src/components/views/settings/ProfileSettings.tsx
@@ -24,7 +24,7 @@ import { OwnProfileStore } from "../../../stores/OwnProfileStore";
 import Modal from "../../../Modal";
 import ErrorDialog from "../dialogs/ErrorDialog";
 import { mediaFromMxc } from "../../../customisations/Media";
-import AccessibleButton from "../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../elements/AccessibleButton";
 import AvatarSetting from "./AvatarSetting";
 import UserIdentifierCustomisations from "../../../customisations/UserIdentifier";
 import { chromeFileInputFix } from "../../../utils/BrowserWorkarounds";
@@ -75,7 +75,7 @@ export default class ProfileSettings extends React.Component<{}, IState> {
         });
     };
 
-    private cancelProfileChanges = async (e: React.MouseEvent): Promise<void> => {
+    private cancelProfileChanges = async (e: ButtonEvent): Promise<void> => {
         e.stopPropagation();
         e.preventDefault();
 
@@ -88,7 +88,7 @@ export default class ProfileSettings extends React.Component<{}, IState> {
         });
     };
 
-    private saveProfile = async (e: React.FormEvent<HTMLFormElement>): Promise<void> => {
+    private saveProfile = async (e: ButtonEvent): Promise<void> => {
         e.stopPropagation();
         e.preventDefault();
 
diff --git a/src/components/views/settings/account/EmailAddresses.tsx b/src/components/views/settings/account/EmailAddresses.tsx
index 08e014c65b..3d72becf33 100644
--- a/src/components/views/settings/account/EmailAddresses.tsx
+++ b/src/components/views/settings/account/EmailAddresses.tsx
@@ -23,7 +23,7 @@ import { MatrixError } from "matrix-js-sdk/src/matrix";
 import { _t, UserFriendlyError } from "../../../../languageHandler";
 import { MatrixClientPeg } from "../../../../MatrixClientPeg";
 import Field from "../../elements/Field";
-import AccessibleButton from "../../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../../elements/AccessibleButton";
 import * as Email from "../../../../email";
 import AddThreepid from "../../../../AddThreepid";
 import Modal from "../../../../Modal";
@@ -59,21 +59,21 @@ export class ExistingEmailAddress extends React.Component<IExistingEmailAddressP
         };
     }
 
-    private onRemove = (e: React.MouseEvent): void => {
+    private onRemove = (e: ButtonEvent): void => {
         e.stopPropagation();
         e.preventDefault();
 
         this.setState({ verifyRemove: true });
     };
 
-    private onDontRemove = (e: React.MouseEvent): void => {
+    private onDontRemove = (e: ButtonEvent): void => {
         e.stopPropagation();
         e.preventDefault();
 
         this.setState({ verifyRemove: false });
     };
 
-    private onActuallyRemove = (e: React.MouseEvent): void => {
+    private onActuallyRemove = (e: ButtonEvent): void => {
         e.stopPropagation();
         e.preventDefault();
 
@@ -196,7 +196,7 @@ export default class EmailAddresses extends React.Component<IProps, IState> {
             });
     };
 
-    private onContinueClick = (e: React.MouseEvent): void => {
+    private onContinueClick = (e: ButtonEvent): void => {
         e.stopPropagation();
         e.preventDefault();
 
diff --git a/src/components/views/settings/account/PhoneNumbers.tsx b/src/components/views/settings/account/PhoneNumbers.tsx
index ede650642d..212148be6e 100644
--- a/src/components/views/settings/account/PhoneNumbers.tsx
+++ b/src/components/views/settings/account/PhoneNumbers.tsx
@@ -22,7 +22,7 @@ import { logger } from "matrix-js-sdk/src/logger";
 import { _t, UserFriendlyError } from "../../../../languageHandler";
 import { MatrixClientPeg } from "../../../../MatrixClientPeg";
 import Field from "../../elements/Field";
-import AccessibleButton from "../../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../../elements/AccessibleButton";
 import AddThreepid from "../../../../AddThreepid";
 import CountryDropdown from "../../auth/CountryDropdown";
 import Modal from "../../../../Modal";
@@ -54,21 +54,21 @@ export class ExistingPhoneNumber extends React.Component<IExistingPhoneNumberPro
         };
     }
 
-    private onRemove = (e: React.MouseEvent): void => {
+    private onRemove = (e: ButtonEvent): void => {
         e.stopPropagation();
         e.preventDefault();
 
         this.setState({ verifyRemove: true });
     };
 
-    private onDontRemove = (e: React.MouseEvent): void => {
+    private onDontRemove = (e: ButtonEvent): void => {
         e.stopPropagation();
         e.preventDefault();
 
         this.setState({ verifyRemove: false });
     };
 
-    private onActuallyRemove = (e: React.MouseEvent): void => {
+    private onActuallyRemove = (e: ButtonEvent): void => {
         e.stopPropagation();
         e.preventDefault();
 
@@ -173,7 +173,7 @@ export default class PhoneNumbers extends React.Component<IProps, IState> {
         });
     };
 
-    private onAddClick = (e: React.MouseEvent | React.FormEvent): void => {
+    private onAddClick = (e: ButtonEvent | React.FormEvent): void => {
         e.stopPropagation();
         e.preventDefault();
 
@@ -199,7 +199,7 @@ export default class PhoneNumbers extends React.Component<IProps, IState> {
             });
     };
 
-    private onContinueClick = (e: React.MouseEvent | React.FormEvent): void => {
+    private onContinueClick = (e: ButtonEvent | React.FormEvent): void => {
         e.stopPropagation();
         e.preventDefault();
 
diff --git a/src/components/views/settings/devices/DeviceDetailHeading.tsx b/src/components/views/settings/devices/DeviceDetailHeading.tsx
index 8a0e054a63..a956316f8c 100644
--- a/src/components/views/settings/devices/DeviceDetailHeading.tsx
+++ b/src/components/views/settings/devices/DeviceDetailHeading.tsx
@@ -14,10 +14,10 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { FormEvent, useEffect, useState } from "react";
+import React, { useEffect, useState } from "react";
 
 import { _t } from "../../../../languageHandler";
-import AccessibleButton from "../../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../../elements/AccessibleButton";
 import Field from "../../elements/Field";
 import LearnMore from "../../elements/LearnMore";
 import Spinner from "../../elements/Spinner";
@@ -41,7 +41,7 @@ const DeviceNameEditor: React.FC<Props & { stopEditing: () => void }> = ({ devic
 
     const onInputChange = (event: React.ChangeEvent<HTMLInputElement>): void => setDeviceName(event.target.value);
 
-    const onSubmit = async (event: FormEvent<HTMLFormElement>): Promise<void> => {
+    const onSubmit = async (event: ButtonEvent): Promise<void> => {
         setIsLoading(true);
         setError(null);
         event.preventDefault();
diff --git a/src/components/views/settings/discovery/EmailAddresses.tsx b/src/components/views/settings/discovery/EmailAddresses.tsx
index f11222af48..8bc13bf187 100644
--- a/src/components/views/settings/discovery/EmailAddresses.tsx
+++ b/src/components/views/settings/discovery/EmailAddresses.tsx
@@ -25,7 +25,7 @@ import { MatrixClientPeg } from "../../../../MatrixClientPeg";
 import Modal from "../../../../Modal";
 import AddThreepid, { Binding } from "../../../../AddThreepid";
 import ErrorDialog, { extractErrorMessageFromError } from "../../dialogs/ErrorDialog";
-import AccessibleButton from "../../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../../elements/AccessibleButton";
 
 /*
 TODO: Improve the UX for everything in here.
@@ -147,7 +147,7 @@ export class EmailAddress extends React.Component<IEmailAddressProps, IEmailAddr
         }
     }
 
-    private onRevokeClick = (e: React.MouseEvent): void => {
+    private onRevokeClick = (e: ButtonEvent): void => {
         e.stopPropagation();
         e.preventDefault();
         this.changeBinding({
@@ -157,7 +157,7 @@ export class EmailAddress extends React.Component<IEmailAddressProps, IEmailAddr
         });
     };
 
-    private onShareClick = (e: React.MouseEvent): void => {
+    private onShareClick = (e: ButtonEvent): void => {
         e.stopPropagation();
         e.preventDefault();
         this.changeBinding({
@@ -167,7 +167,7 @@ export class EmailAddress extends React.Component<IEmailAddressProps, IEmailAddr
         });
     };
 
-    private onContinueClick = async (e: React.MouseEvent): Promise<void> => {
+    private onContinueClick = async (e: ButtonEvent): Promise<void> => {
         e.stopPropagation();
         e.preventDefault();
 
diff --git a/src/components/views/settings/discovery/PhoneNumbers.tsx b/src/components/views/settings/discovery/PhoneNumbers.tsx
index 9ae1719259..7c61db8cd3 100644
--- a/src/components/views/settings/discovery/PhoneNumbers.tsx
+++ b/src/components/views/settings/discovery/PhoneNumbers.tsx
@@ -26,7 +26,7 @@ import Modal from "../../../../Modal";
 import AddThreepid, { Binding } from "../../../../AddThreepid";
 import ErrorDialog, { extractErrorMessageFromError } from "../../dialogs/ErrorDialog";
 import Field from "../../elements/Field";
-import AccessibleButton from "../../elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../../elements/AccessibleButton";
 
 /*
 TODO: Improve the UX for everything in here.
@@ -154,7 +154,7 @@ export class PhoneNumber extends React.Component<IPhoneNumberProps, IPhoneNumber
         }
     }
 
-    private onRevokeClick = (e: React.MouseEvent): void => {
+    private onRevokeClick = (e: ButtonEvent): void => {
         e.stopPropagation();
         e.preventDefault();
         this.changeBinding({
@@ -164,7 +164,7 @@ export class PhoneNumber extends React.Component<IPhoneNumberProps, IPhoneNumber
         });
     };
 
-    private onShareClick = (e: React.MouseEvent): void => {
+    private onShareClick = (e: ButtonEvent): void => {
         e.stopPropagation();
         e.preventDefault();
         this.changeBinding({
@@ -180,7 +180,7 @@ export class PhoneNumber extends React.Component<IPhoneNumberProps, IPhoneNumber
         });
     };
 
-    private onContinueClick = async (e: React.MouseEvent | React.FormEvent): Promise<void> => {
+    private onContinueClick = async (e: ButtonEvent | React.FormEvent): Promise<void> => {
         e.stopPropagation();
         e.preventDefault();
 
diff --git a/src/components/views/settings/tabs/room/GeneralRoomSettingsTab.tsx b/src/components/views/settings/tabs/room/GeneralRoomSettingsTab.tsx
index 631af29fa2..fa5c65ab89 100644
--- a/src/components/views/settings/tabs/room/GeneralRoomSettingsTab.tsx
+++ b/src/components/views/settings/tabs/room/GeneralRoomSettingsTab.tsx
@@ -41,7 +41,7 @@ interface IState {
 
 export default class GeneralRoomSettingsTab extends React.Component<IProps, IState> {
     public static contextType = MatrixClientContext;
-    public context: ContextType<typeof MatrixClientContext>;
+    public context!: ContextType<typeof MatrixClientContext>;
 
     public constructor(props: IProps, context: ContextType<typeof MatrixClientContext>) {
         super(props, context);
diff --git a/src/components/views/settings/tabs/room/NotificationSettingsTab.tsx b/src/components/views/settings/tabs/room/NotificationSettingsTab.tsx
index f1304d44ed..627971eaf3 100644
--- a/src/components/views/settings/tabs/room/NotificationSettingsTab.tsx
+++ b/src/components/views/settings/tabs/room/NotificationSettingsTab.tsx
@@ -70,7 +70,7 @@ export default class NotificationsSettingsTab extends React.Component<IProps, IS
         };
     }
 
-    private triggerUploader = async (e: React.MouseEvent): Promise<void> => {
+    private triggerUploader = async (e: ButtonEvent): Promise<void> => {
         e.stopPropagation();
         e.preventDefault();
 
@@ -91,7 +91,7 @@ export default class NotificationsSettingsTab extends React.Component<IProps, IS
         });
     };
 
-    private onClickSaveSound = async (e: React.MouseEvent): Promise<void> => {
+    private onClickSaveSound = async (e: ButtonEvent): Promise<void> => {
         e.stopPropagation();
         e.preventDefault();
 
@@ -133,7 +133,7 @@ export default class NotificationsSettingsTab extends React.Component<IProps, IS
         });
     }
 
-    private clearSound = (e: React.MouseEvent): void => {
+    private clearSound = (e: ButtonEvent): void => {
         e.stopPropagation();
         e.preventDefault();
         SettingsStore.setValue("notificationSound", this.props.roomId, SettingLevel.ROOM_ACCOUNT, null);
diff --git a/src/indexing/EventIndex.ts b/src/indexing/EventIndex.ts
index 84c0a3ec20..c2acab5b00 100644
--- a/src/indexing/EventIndex.ts
+++ b/src/indexing/EventIndex.ts
@@ -193,7 +193,7 @@ export default class EventIndex extends EventEmitter {
     private onRoomTimeline = async (
         ev: MatrixEvent,
         room: Room | undefined,
-        toStartOfTimeline: boolean,
+        toStartOfTimeline: boolean | undefined,
         removed: boolean,
         data: IRoomTimelineData,
     ): Promise<void> => {
diff --git a/src/settings/handlers/AccountSettingsHandler.ts b/src/settings/handlers/AccountSettingsHandler.ts
index 8e35b2554f..30424c3a16 100644
--- a/src/settings/handlers/AccountSettingsHandler.ts
+++ b/src/settings/handlers/AccountSettingsHandler.ts
@@ -50,7 +50,7 @@ export default class AccountSettingsHandler extends MatrixClientBackedSettingsHa
         newClient.on(ClientEvent.AccountData, this.onAccountData);
     }
 
-    private onAccountData = (event: MatrixEvent, prevEvent: MatrixEvent): void => {
+    private onAccountData = (event: MatrixEvent, prevEvent?: MatrixEvent): void => {
         if (event.getType() === "org.matrix.preview_urls") {
             let val = event.getContent()["disable"];
             if (typeof val !== "boolean") {
diff --git a/src/settings/handlers/RoomAccountSettingsHandler.ts b/src/settings/handlers/RoomAccountSettingsHandler.ts
index 5e29330329..700bc7d397 100644
--- a/src/settings/handlers/RoomAccountSettingsHandler.ts
+++ b/src/settings/handlers/RoomAccountSettingsHandler.ts
@@ -44,7 +44,7 @@ export default class RoomAccountSettingsHandler extends MatrixClientBackedSettin
         newClient.on(RoomEvent.AccountData, this.onAccountData);
     }
 
-    private onAccountData = (event: MatrixEvent, room: Room, prevEvent: MatrixEvent): void => {
+    private onAccountData = (event: MatrixEvent, room: Room, prevEvent?: MatrixEvent): void => {
         const roomId = room.roomId;
 
         if (event.getType() === "org.matrix.room.preview_urls") {
@@ -58,7 +58,7 @@ export default class RoomAccountSettingsHandler extends MatrixClientBackedSettin
             this.watchers.notifyUpdate("urlPreviewsEnabled", roomId, SettingLevel.ROOM_ACCOUNT, val);
         } else if (event.getType() === DEFAULT_SETTINGS_EVENT_TYPE) {
             // Figure out what changed and fire those updates
-            const prevContent = prevEvent ? prevEvent.getContent() : {};
+            const prevContent = prevEvent?.getContent() ?? {};
             const changedSettings = objectKeyChanges<Record<string, any>>(prevContent, event.getContent());
             for (const settingName of changedSettings) {
                 const val = event.getContent()[settingName];
diff --git a/src/settings/handlers/RoomSettingsHandler.ts b/src/settings/handlers/RoomSettingsHandler.ts
index a7c6408ce9..48370df36c 100644
--- a/src/settings/handlers/RoomSettingsHandler.ts
+++ b/src/settings/handlers/RoomSettingsHandler.ts
@@ -43,7 +43,7 @@ export default class RoomSettingsHandler extends MatrixClientBackedSettingsHandl
         newClient.on(RoomStateEvent.Events, this.onEvent);
     }
 
-    private onEvent = (event: MatrixEvent, state: RoomState, prevEvent: MatrixEvent): void => {
+    private onEvent = (event: MatrixEvent, state: RoomState, prevEvent: MatrixEvent | null): void => {
         const roomId = event.getRoomId()!;
         const room = this.client.getRoom(roomId);
 
@@ -67,7 +67,7 @@ export default class RoomSettingsHandler extends MatrixClientBackedSettingsHandl
             this.watchers.notifyUpdate("urlPreviewsEnabled", roomId, SettingLevel.ROOM, val);
         } else if (event.getType() === DEFAULT_SETTINGS_EVENT_TYPE) {
             // Figure out what changed and fire those updates
-            const prevContent = prevEvent ? prevEvent.getContent() : {};
+            const prevContent = prevEvent?.getContent() ?? {};
             const changedSettings = objectKeyChanges<Record<string, any>>(prevContent, event.getContent());
             for (const settingName of changedSettings) {
                 this.watchers.notifyUpdate(settingName, roomId, SettingLevel.ROOM, event.getContent()[settingName]);
diff --git a/src/stores/AutoRageshakeStore.ts b/src/stores/AutoRageshakeStore.ts
index 2d20b95da4..a5d6b0068b 100644
--- a/src/stores/AutoRageshakeStore.ts
+++ b/src/stores/AutoRageshakeStore.ts
@@ -142,7 +142,11 @@ export default class AutoRageshakeStore extends AsyncStoreWithClient<IState> {
         }
     }
 
-    private async onSyncStateChange(_state: SyncState, _prevState: SyncState, data?: ISyncStateData): Promise<void> {
+    private async onSyncStateChange(
+        _state: SyncState,
+        _prevState: SyncState | null,
+        data?: ISyncStateData,
+    ): Promise<void> {
         if (!this.state.initialSyncCompleted) {
             await this.updateState({ initialSyncCompleted: !!data?.nextSyncToken });
         }
diff --git a/src/toasts/IncomingLegacyCallToast.tsx b/src/toasts/IncomingLegacyCallToast.tsx
index 26ea393332..33a904afe7 100644
--- a/src/toasts/IncomingLegacyCallToast.tsx
+++ b/src/toasts/IncomingLegacyCallToast.tsx
@@ -26,7 +26,7 @@ import { MatrixClientPeg } from "../MatrixClientPeg";
 import { _t } from "../languageHandler";
 import RoomAvatar from "../components/views/avatars/RoomAvatar";
 import AccessibleTooltipButton from "../components/views/elements/AccessibleTooltipButton";
-import AccessibleButton from "../components/views/elements/AccessibleButton";
+import AccessibleButton, { ButtonEvent } from "../components/views/elements/AccessibleButton";
 
 export const getIncomingLegacyCallToastKey = (callId: string): string => `call_${callId}`;
 
@@ -73,17 +73,17 @@ export default class IncomingLegacyCallToast extends React.Component<IProps, ISt
         this.setState({ silenced: LegacyCallHandler.instance.isCallSilenced(this.props.call.callId) });
     };
 
-    private onAnswerClick = (e: React.MouseEvent): void => {
+    private onAnswerClick = (e: ButtonEvent): void => {
         e.stopPropagation();
         LegacyCallHandler.instance.answerCall(this.roomId);
     };
 
-    private onRejectClick = (e: React.MouseEvent): void => {
+    private onRejectClick = (e: ButtonEvent): void => {
         e.stopPropagation();
         LegacyCallHandler.instance.hangupOrReject(this.roomId, true);
     };
 
-    private onSilenceClick = (e: React.MouseEvent): void => {
+    private onSilenceClick = (e: ButtonEvent): void => {
         e.stopPropagation();
         const callId = this.props.call.callId;
         this.state.silenced
diff --git a/src/utils/connection.ts b/src/utils/connection.ts
index 55eed17d47..0a0569fc98 100644
--- a/src/utils/connection.ts
+++ b/src/utils/connection.ts
@@ -22,7 +22,7 @@ import { SyncState } from "matrix-js-sdk/src/sync";
  * @param callback The callback to be called on reconnect
  */
 export const createReconnectedListener = (callback: () => void): ClientEventHandlerMap[ClientEvent.Sync] => {
-    return (syncState: SyncState, prevState: SyncState) => {
+    return (syncState: SyncState, prevState: SyncState | null) => {
         if (syncState !== SyncState.Error && prevState !== syncState) {
             // Consider the client reconnected if there is no error with syncing.
             // This means the state could be RECONNECTING, SYNCING, PREPARED or CATCHUP.
diff --git a/test/components/views/rooms/MessageComposer-test.tsx b/test/components/views/rooms/MessageComposer-test.tsx
index e076b8ae4a..b4f5b696db 100644
--- a/test/components/views/rooms/MessageComposer-test.tsx
+++ b/test/components/views/rooms/MessageComposer-test.tsx
@@ -268,9 +268,11 @@ describe("MessageComposer", () => {
             let resizeCallback: Function;
 
             beforeEach(() => {
-                jest.spyOn(UIStore.instance, "on").mockImplementation((_event: string, listener: Function): any => {
-                    resizeCallback = listener;
-                });
+                jest.spyOn(UIStore.instance, "on").mockImplementation(
+                    (_event: string | symbol, listener: Function): any => {
+                        resizeCallback = listener;
+                    },
+                );
             });
 
             describe("when a non-resize event occurred in UIStore", () => {
diff --git a/test/voice-broadcast/stores/VoiceBroadcastPlaybacksStore-test.ts b/test/voice-broadcast/stores/VoiceBroadcastPlaybacksStore-test.ts
index 889e94a093..375851ee8b 100644
--- a/test/voice-broadcast/stores/VoiceBroadcastPlaybacksStore-test.ts
+++ b/test/voice-broadcast/stores/VoiceBroadcastPlaybacksStore-test.ts
@@ -40,7 +40,7 @@ describe("VoiceBroadcastPlaybacksStore", () => {
     let playback1: VoiceBroadcastPlayback;
     let playback2: VoiceBroadcastPlayback;
     let playbacks: VoiceBroadcastPlaybacksStore;
-    let onCurrentChanged: (playback: VoiceBroadcastPlayback) => void;
+    let onCurrentChanged: (playback: VoiceBroadcastPlayback | null) => void;
 
     beforeEach(() => {
         client = stubClient();
diff --git a/test/voice-broadcast/stores/VoiceBroadcastRecordingsStore-test.ts b/test/voice-broadcast/stores/VoiceBroadcastRecordingsStore-test.ts
index f8a9cc9448..ae255405a5 100644
--- a/test/voice-broadcast/stores/VoiceBroadcastRecordingsStore-test.ts
+++ b/test/voice-broadcast/stores/VoiceBroadcastRecordingsStore-test.ts
@@ -35,7 +35,7 @@ describe("VoiceBroadcastRecordingsStore", () => {
     let recording: VoiceBroadcastRecording;
     let otherRecording: VoiceBroadcastRecording;
     let recordings: VoiceBroadcastRecordingsStore;
-    let onCurrentChanged: (recording: VoiceBroadcastRecording) => void;
+    let onCurrentChanged: (recording: VoiceBroadcastRecording | null) => void;
 
     beforeEach(() => {
         client = stubClient();