diff --git a/syncapi/storage/shared/storage_consumer.go b/syncapi/storage/shared/storage_consumer.go
index 5bd3b1f01..799e3d166 100644
--- a/syncapi/storage/shared/storage_consumer.go
+++ b/syncapi/storage/shared/storage_consumer.go
@@ -507,8 +507,20 @@ func (d *Database) CleanSendToDeviceUpdates(
 
 // getMembershipFromEvent returns the value of content.membership iff the event is a state event
 // with type 'm.room.member' and state_key of userID. Otherwise, an empty string is returned.
-func getMembershipFromEvent(ev gomatrixserverlib.PDU, userID string) (string, string) {
-	if ev.Type() != "m.room.member" || !ev.StateKeyEquals(userID) {
+func getMembershipFromEvent(ctx context.Context, ev gomatrixserverlib.PDU, userID string, rsAPI api.SyncRoomserverAPI) (string, string) {
+	if ev.StateKey() == nil || *ev.StateKey() == "" {
+		return "", ""
+	}
+	fullUser, err := spec.NewUserID(userID, true)
+	if err != nil {
+		return "", ""
+	}
+	senderID, err := rsAPI.QuerySenderIDForUser(ctx, ev.RoomID(), *fullUser)
+	if err != nil {
+		return "", ""
+	}
+
+	if ev.Type() != "m.room.member" || !ev.StateKeyEquals(string(senderID)) {
 		return "", ""
 	}
 	membership, err := ev.Membership()
diff --git a/syncapi/storage/shared/storage_sync.go b/syncapi/storage/shared/storage_sync.go
index df9613850..8e79b71df 100644
--- a/syncapi/storage/shared/storage_sync.go
+++ b/syncapi/storage/shared/storage_sync.go
@@ -430,7 +430,7 @@ func (d *DatabaseTransaction) GetStateDeltas(
 		for _, ev := range stateStreamEvents {
 			// Look for our membership in the state events and skip over any
 			// membership events that are not related to us.
-			membership, prevMembership := getMembershipFromEvent(ev.PDU, userID)
+			membership, prevMembership := getMembershipFromEvent(ctx, ev.PDU, userID, rsAPI)
 			if membership == "" {
 				continue
 			}
@@ -556,7 +556,7 @@ func (d *DatabaseTransaction) GetStateDeltasForFullStateSync(
 
 	for roomID, stateStreamEvents := range state {
 		for _, ev := range stateStreamEvents {
-			if membership, _ := getMembershipFromEvent(ev.PDU, userID); membership != "" {
+			if membership, _ := getMembershipFromEvent(ctx, ev.PDU, userID, rsAPI); membership != "" {
 				if membership != spec.Join { // We've already added full state for all joined rooms above.
 					deltas[roomID] = types.StateDelta{
 						Membership:    membership,