diff --git a/src/UserActivity.ts b/src/UserActivity.ts
index 9217aca3c0..44c8abb2c7 100644
--- a/src/UserActivity.ts
+++ b/src/UserActivity.ts
@@ -182,11 +182,11 @@ export default class UserActivity {
         this.activeRecentlyTimeout.abort();
     };
 
-    private onUserActivity = (event: MouseEvent): void => {
+    private onUserActivity = (event: Event): void => {
         // ignore anything if the window isn't focused
         if (!this.document.hasFocus()) return;
 
-        if (event.screenX && event.type === "mousemove") {
+        if (event.type === "mousemove" && this.isMouseEvent(event)) {
             if (event.screenX === this.lastScreenX && event.screenY === this.lastScreenY) {
                 // mouse hasn't actually moved
                 return;
@@ -223,4 +223,8 @@ export default class UserActivity {
         }
         attachedTimers.forEach((t) => t.abort());
     }
+
+    private isMouseEvent(event: Event): event is MouseEvent {
+        return event.type.startsWith("mouse");
+    }
 }
diff --git a/src/VoipUserMapper.ts b/src/VoipUserMapper.ts
index 7a163350db..ae5170d6e4 100644
--- a/src/VoipUserMapper.ts
+++ b/src/VoipUserMapper.ts
@@ -38,7 +38,7 @@ export default class VoipUserMapper {
         return window.mxVoipUserMapper;
     }
 
-    private async userToVirtualUser(userId: string): Promise<string> {
+    private async userToVirtualUser(userId: string): Promise<string | null> {
         const results = await LegacyCallHandler.instance.sipVirtualLookup(userId);
         if (results.length === 0 || !results[0].fields.lookup_success) return null;
         return results[0].userid;
@@ -59,11 +59,11 @@ export default class VoipUserMapper {
         if (!virtualUser) return null;
 
         const virtualRoomId = await ensureVirtualRoomExists(MatrixClientPeg.get(), virtualUser, roomId);
-        MatrixClientPeg.get().setRoomAccountData(virtualRoomId, VIRTUAL_ROOM_EVENT_TYPE, {
+        MatrixClientPeg.get().setRoomAccountData(virtualRoomId!, VIRTUAL_ROOM_EVENT_TYPE, {
             native_room: roomId,
         });
 
-        this.virtualToNativeRoomIdCache.set(virtualRoomId, roomId);
+        this.virtualToNativeRoomIdCache.set(virtualRoomId!, roomId);
 
         return virtualRoomId;
     }
@@ -121,8 +121,12 @@ export default class VoipUserMapper {
         if (!LegacyCallHandler.instance.getSupportsVirtualRooms()) return;
 
         const inviterId = invitedRoom.getDMInviter();
+        if (!inviterId) {
+            logger.error("Could not find DM inviter for room id: " + invitedRoom.roomId);
+        }
+
         logger.log(`Checking virtual-ness of room ID ${invitedRoom.roomId}, invited by ${inviterId}`);
-        const result = await LegacyCallHandler.instance.sipNativeLookup(inviterId);
+        const result = await LegacyCallHandler.instance.sipNativeLookup(inviterId!);
         if (result.length === 0) {
             return;
         }
diff --git a/src/WhoIsTyping.ts b/src/WhoIsTyping.ts
index 01e7b2e4f7..d4a43636ce 100644
--- a/src/WhoIsTyping.ts
+++ b/src/WhoIsTyping.ts
@@ -21,11 +21,11 @@ import { MatrixClientPeg } from "./MatrixClientPeg";
 import { _t } from "./languageHandler";
 
 export function usersTypingApartFromMeAndIgnored(room: Room): RoomMember[] {
-    return usersTyping(room, [MatrixClientPeg.get().getUserId()].concat(MatrixClientPeg.get().getIgnoredUsers()));
+    return usersTyping(room, [MatrixClientPeg.get().getUserId()!].concat(MatrixClientPeg.get().getIgnoredUsers()));
 }
 
 export function usersTypingApartFromMe(room: Room): RoomMember[] {
-    return usersTyping(room, [MatrixClientPeg.get().getUserId()]);
+    return usersTyping(room, [MatrixClientPeg.get().getUserId()!]);
 }
 
 /**
@@ -36,7 +36,7 @@ export function usersTypingApartFromMe(room: Room): RoomMember[] {
  * @returns {RoomMember[]} list of user objects who are typing.
  */
 export function usersTyping(room: Room, exclude: string[] = []): RoomMember[] {
-    const whoIsTyping = [];
+    const whoIsTyping: RoomMember[] = [];
 
     const memberKeys = Object.keys(room.currentState.members);
     for (const userId of memberKeys) {
diff --git a/src/verification.ts b/src/verification.ts
index 11ece17e90..c7cdd8073a 100644
--- a/src/verification.ts
+++ b/src/verification.ts
@@ -120,7 +120,7 @@ function setRightPanel(state: IRightPanelCardState): void {
     }
 }
 
-export function pendingVerificationRequestForUser(user: User | RoomMember): VerificationRequest {
+export function pendingVerificationRequestForUser(user: User | RoomMember): VerificationRequest | undefined {
     const cli = MatrixClientPeg.get();
     const dmRoom = findDMForUser(cli, user.userId);
     if (dmRoom) {