diff --git a/src/UserActivity.js b/src/UserActivity.js
index 6b918f0729..8b136c0bcc 100644
--- a/src/UserActivity.js
+++ b/src/UserActivity.js
@@ -33,7 +33,9 @@ class UserActivity {
         document.onkeypress = this._onUserActivity.bind(this);
         // can't use document.scroll here because that's only the document
         // itself being scrolled. Need to use addEventListener's useCapture.
-        window.addEventListener('scroll', this._onUserActivity.bind(this), true);
+        // also this needs to be the wheel event, not scroll, as scroll is
+        // fired when the view scrolls down for a new message.
+        window.addEventListener('wheel', this._onUserActivity.bind(this), true);
         this.lastActivityAtTs = new Date().getTime();
         this.lastDispatchAtTs = 0;
     }
@@ -44,11 +46,11 @@ class UserActivity {
     stop() {
         document.onmousemove = undefined;
         document.onkeypress = undefined;
-        window.removeEventListener('scroll', this._onUserActivity.bind(this), true);
+        window.removeEventListener('wheel', this._onUserActivity.bind(this), true);
     }
 
     _onUserActivity(event) {
-        if (event.screenX) {
+        if (event.screenX && event.type == "mousemove") {
             if (event.screenX === this.lastScreenX &&
                 event.screenY === this.lastScreenY)
             {