diff --git a/apps/web/src/stores/RoomViewStore.tsx b/apps/web/src/stores/RoomViewStore.tsx
index 73050916619..2d2063534a7 100644
--- a/apps/web/src/stores/RoomViewStore.tsx
+++ b/apps/web/src/stores/RoomViewStore.tsx
@@ -148,7 +148,8 @@ export class RoomViewStore extends EventEmitter {
     // another RVS via INITIAL_STATE as they share the same underlying object. Mostly relevant for tests.
     private state = utils.deepCopy(INITIAL_STATE);
 
-    private dis?: MatrixDispatcher;
+    // this is defacto always assigned as `resetDispatcher` is called in the constructor.
+    private dis!: MatrixDispatcher;
     private dispatchToken?: string;
 
     public constructor(
@@ -195,7 +196,7 @@ export class RoomViewStore extends EventEmitter {
 
             // Fired so we can reduce dependency on event emitters to this store, which is relatively
             // central to the application and can easily cause import cycles.
-            this.dis?.dispatch<ActiveRoomChangedPayload>({
+            this.dis.dispatch<ActiveRoomChangedPayload>({
                 action: Action.ActiveRoomChanged,
                 oldRoomId: lastRoomId,
                 newRoomId: this.state.roomId,
@@ -302,7 +303,7 @@ export class RoomViewStore extends EventEmitter {
                         // if the room is displayed in a module, we don't want to change the room view
                         if (roomId && this.isRoomDisplayedInModule(roomId)) return;
 
-                        this.dis?.dispatch<ViewRoomPayload>({
+                        this.dis.dispatch<ViewRoomPayload>({
                             action: Action.ViewRoom,
                             room_id: payload.event.getRoomId(),
                             replyingToEvent: payload.event,
@@ -415,7 +416,7 @@ export class RoomViewStore extends EventEmitter {
                 await this.stores.slidingSyncManager.setRoomVisible(payload.room_id);
 
                 // Re-fire the payload: we won't re-process it because the prev room ID == payload room ID now
-                this.dis?.dispatch({
+                this.dis.dispatch({
                     ...payload,
                 });
                 return;
@@ -466,7 +467,7 @@ export class RoomViewStore extends EventEmitter {
                         viaServers: payload.via_servers,
                     };
                 }
-                this.dis?.dispatch<JoinRoomPayload>(joinPayload);
+                this.dis.dispatch<JoinRoomPayload>(joinPayload);
             }
 
             if (room) {
@@ -505,7 +506,7 @@ export class RoomViewStore extends EventEmitter {
                     viaServers = result.servers;
                 } catch (err) {
                     logger.error("RVS failed to get room id for alias: ", err);
-                    this.dis?.dispatch<ViewRoomErrorPayload>({
+                    this.dis.dispatch<ViewRoomErrorPayload>({
                         action: Action.ViewRoomError,
                         room_id: null,
                         room_alias: payload.room_alias,
@@ -516,7 +517,7 @@ export class RoomViewStore extends EventEmitter {
             }
 
             // Re-fire the payload with the newly found room_id
-            this.dis?.dispatch({
+            this.dis.dispatch({
                 ...payload,
                 room_id: roomId,
                 via_servers: viaServers,
@@ -545,9 +546,22 @@ export class RoomViewStore extends EventEmitter {
         });
 
         // take a copy of roomAlias, roomId & viaServers as they may change by the time the join is complete
-        const { roomAlias, roomId = payload.roomId, viaServers = [] } = this.state;
+        const { roomAlias, viaServers = [] } = this.state;
+        // fall back to the payload's roomId explicitly since it is always the room we were asked to join
+        const roomId = this.state.roomId ?? payload.roomId;
         // prefer the room alias if we have one as it allows joining over federation even with no viaServers
-        const address = roomAlias || roomId!;
+        const address = roomAlias || roomId;
+
+        if (!address) {
+            logger.error("Cannot join room: no room ID or alias to join", payload);
+            this.dis.dispatch<JoinRoomErrorPayload>({
+                action: Action.JoinRoomError,
+                roomId,
+                err: new UserFriendlyError("room|error_join_unknown", { cause: undefined }),
+                canAskToJoin: payload.canAskToJoin,
+            });
+            return;
+        }
 
         const joinOpts: IJoinRoomOpts = {
             viaServers,
@@ -568,14 +582,14 @@ export class RoomViewStore extends EventEmitter {
             // We do *not* clear the 'joining' flag because the Room object and/or our 'joined' member event may not
             // have come down the sync stream yet, and that's the point at which we'd consider the user joined to the
             // room.
-            this.dis?.dispatch<JoinRoomReadyPayload>({
+            this.dis.dispatch<JoinRoomReadyPayload>({
                 action: Action.JoinRoomReady,
-                roomId: roomId!,
+                roomId,
                 metricsTrigger: payload.metricsTrigger,
             });
         } catch (err) {
             logger.error("Error thrown while handling joinRoom", err);
-            this.dis?.dispatch<JoinRoomErrorPayload>({
+            this.dis.dispatch<JoinRoomErrorPayload>({
                 action: Action.JoinRoomError,
                 roomId,
                 err: err instanceof Error ? err : new UserFriendlyError("room|error_join_unknown", { cause: err }),
@@ -583,7 +597,7 @@ export class RoomViewStore extends EventEmitter {
             });
 
             if (payload.canAskToJoin && err instanceof MatrixError && err.httpStatus === 403) {
-                this.dis?.dispatch({ action: Action.PromptAskToJoin });
+                this.dis.dispatch({ action: Action.PromptAskToJoin });
             }
         }
     }
@@ -665,7 +679,7 @@ export class RoomViewStore extends EventEmitter {
      */
     public resetDispatcher(dis: MatrixDispatcher): void {
         if (this.dispatchToken) {
-            this.dis?.unregister(this.dispatchToken);
+            this.dis.unregister(this.dispatchToken);
         }
         this.dis = dis;
         if (dis) {