diff --git a/src/useReactions.test.tsx b/src/useReactions.test.tsx
index 99db2619..79caeb0a 100644
--- a/src/useReactions.test.tsx
+++ b/src/useReactions.test.tsx
@@ -99,9 +99,12 @@ export class MockRTCSession extends EventEmitter {
   }
 }
 
-function createReaction(parentMemberEvent: string): MatrixEvent {
+function createReaction(
+  parentMemberEvent: string,
+  overridenSender?: string,
+): MatrixEvent {
   return new MatrixEvent({
-    sender: membership[parentMemberEvent],
+    sender: overridenSender ?? membership[parentMemberEvent],
     type: EventType.Reaction,
     origin_server_ts: new Date().getTime(),
     content: {
@@ -140,15 +143,20 @@ export class MockRoom extends EventEmitter {
     return {
       getChildEventsForEvent: (membershipEventId: string) => ({
         getRelations: (): MatrixEvent[] => {
-          const sender = membership[membershipEventId];
-          return this.existingRelations.filter((r) => r.getSender() === sender);
+          return this.existingRelations.filter(
+            (r) =>
+              r.getContent()["m.relates_to"]?.event_id === membershipEventId,
+          );
         },
       }),
     } as unknown as Room["relations"];
   }
 
-  public testSendReaction(parentMemberEvent: string): string {
-    const evt = createReaction(parentMemberEvent);
+  public testSendReaction(
+    parentMemberEvent: string,
+    overridenSender?: string,
+  ): string {
+    const evt = createReaction(parentMemberEvent, overridenSender);
     this.emit(RoomEvent.Timeline, evt, this, undefined, false, {
       timeline: new EventTimeline(new EventTimelineSet(undefined)),
     });
@@ -238,4 +246,23 @@ describe("useReactions", () => {
     });
     expect(queryByRole("list")?.children).to.have.lengthOf(0);
   });
+  test("ignores invalid sender for historic event", () => {
+    const room = new MockRoom([
+      createReaction(memberEventAlice, memberUserIdBob),
+    ]);
+    const rtcSession = new MockRTCSession(room);
+    const { queryByRole } = render(
+      <TestComponentWrapper rtcSession={rtcSession} />,
+    );
+    expect(queryByRole("list")?.children).to.have.lengthOf(0);
+  });
+  test("ignores invalid sender for new event", async () => {
+    const room = new MockRoom([]);
+    const rtcSession = new MockRTCSession(room);
+    const { queryByRole } = render(
+      <TestComponentWrapper rtcSession={rtcSession} />,
+    );
+    await act(() => room.testSendReaction(memberEventAlice, memberUserIdBob));
+    expect(queryByRole("list")?.children).to.have.lengthOf(0);
+  });
 });
diff --git a/src/useReactions.tsx b/src/useReactions.tsx
index 6aac4043..342c43e1 100644
--- a/src/useReactions.tsx
+++ b/src/useReactions.tsx
@@ -113,14 +113,17 @@ export const ReactionsProvider = ({
   useEffect(() => {
     // Fetches the first reaction for a given event. We assume no more than
     // one reaction on an event here.
-    const getLastReactionEvent = (eventId: string): MatrixEvent | undefined => {
+    const getLastReactionEvent = (
+      eventId: string,
+      expectedSender: string,
+    ): MatrixEvent | undefined => {
       const relations = room.relations.getChildEventsForEvent(
         eventId,
         RelationType.Annotation,
         EventType.Reaction,
       );
       const allEvents = relations?.getRelations() ?? [];
-      return allEvents.find((u) => u.sender === myUserId);
+      return allEvents.find((u) => u.event.sender === expectedSender);
     };
 
     // Remove any raised hands for users no longer joined to the call.
@@ -144,7 +147,7 @@ export const ReactionsProvider = ({
         // was raised, reset.
         removeRaisedHand(m.sender);
       }
-      const reaction = getLastReactionEvent(m.eventId);
+      const reaction = getLastReactionEvent(m.eventId, m.sender);
       const eventId = reaction?.getId();
       if (!eventId) {
         continue;
@@ -160,14 +163,10 @@ export const ReactionsProvider = ({
         }
       }
     }
-  }, [
-    room,
-    memberships,
-    myUserId,
-    raisedHands,
-    addRaisedHand,
-    removeRaisedHand,
-  ]);
+    // Ignoring raisedHands here because we don't want to trigger each time the raised
+    // hands set is updated.
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [room, memberships, myUserId, addRaisedHand, removeRaisedHand]);
 
   // This effect handles any *live* reaction/redactions in the room.
   useEffect(() => {