diff --git a/src/components/structures/ThreadView.tsx b/src/components/structures/ThreadView.tsx
index f15318d572..f88b34e8bc 100644
--- a/src/components/structures/ThreadView.tsx
+++ b/src/components/structures/ThreadView.tsx
@@ -214,7 +214,12 @@ export default class ThreadView extends React.Component<IProps, IState> {
         let thread = this.props.room.getThread(eventId);
 
         if (!thread) {
-            thread = this.props.room.createThread(eventId, mxEv, [mxEv], true);
+            const events = [];
+            // if the event is still being sent, don't include it in the Thread yet - otherwise the timeline panel
+            // will attempt to show it twice (once as a regular event, once as a pending event) and everything will
+            // blow up
+            if (mxEv.status === null) events.push(mxEv);
+            thread = this.props.room.createThread(eventId, mxEv, events, true);
         }
 
         this.updateThread(thread);
diff --git a/test/components/structures/ThreadView-test.tsx b/test/components/structures/ThreadView-test.tsx
index fb5440d768..857137a5f2 100644
--- a/test/components/structures/ThreadView-test.tsx
+++ b/test/components/structures/ThreadView-test.tsx
@@ -19,7 +19,7 @@ import userEvent from "@testing-library/user-event";
 import { mocked } from "jest-mock";
 import { MsgType, RelationType } from "matrix-js-sdk/src/@types/event";
 import { MatrixClient, PendingEventOrdering } from "matrix-js-sdk/src/client";
-import { MatrixEvent } from "matrix-js-sdk/src/models/event";
+import { EventStatus, MatrixEvent } from "matrix-js-sdk/src/models/event";
 import { Room } from "matrix-js-sdk/src/models/room";
 import { THREAD_RELATION_TYPE } from "matrix-js-sdk/src/models/thread";
 import React, { useState } from "react";
@@ -35,7 +35,7 @@ import DMRoomMap from "../../../src/utils/DMRoomMap";
 import ResizeNotifier from "../../../src/utils/ResizeNotifier";
 import { mockPlatformPeg } from "../../test-utils/platform";
 import { getRoomContext } from "../../test-utils/room";
-import { stubClient } from "../../test-utils/test-utils";
+import { mkMessage, stubClient } from "../../test-utils/test-utils";
 import { mkThread } from "../../test-utils/threads";
 
 describe("ThreadView", () => {
@@ -135,6 +135,24 @@ describe("ThreadView", () => {
         jest.spyOn(DMRoomMap.shared(), "getUserIdForRoomId").mockReturnValue(SENDER);
     });
 
+    it("does not include pending root event in the timeline twice", async () => {
+        rootEvent = mkMessage({
+            user: mockClient.getUserId()!,
+            event: true,
+            room: room.roomId,
+            msg: "root event message " + Math.random(),
+        });
+
+        rootEvent.status = EventStatus.SENDING;
+        rootEvent.setTxnId("1234");
+        room.addPendingEvent(rootEvent, "1234");
+        room.updatePendingEvent(rootEvent, EventStatus.SENT, rootEvent.getId());
+
+        const { container } = await getComponent();
+        const tiles = container.getElementsByClassName("mx_EventTile");
+        expect(tiles.length).toEqual(1);
+    });
+
     it("sends a message with the correct fallback", async () => {
         const { container } = await getComponent();
 
diff --git a/test/test-utils/threads.ts b/test/test-utils/threads.ts
index 8c7c658cfc..0bc6ea8b0a 100644
--- a/test/test-utils/threads.ts
+++ b/test/test-utils/threads.ts
@@ -136,10 +136,6 @@ export const mkThread = ({
 
     const thread = room.createThread(rootEvent.getId()!, rootEvent, events, true);
 
-    events.forEach((event) => {
-        thread.timeline.push(event);
-    });
-
     // So that we do not have to mock the thread loading
     thread.initialEventsFetched = true;