diff --git a/roomserver/internal/input/input_membership.go b/roomserver/internal/input/input_membership.go
index 54cad14f7..09c65dfe9 100644
--- a/roomserver/internal/input/input_membership.go
+++ b/roomserver/internal/input/input_membership.go
@@ -18,7 +18,6 @@ import (
 	"context"
 	"fmt"
 
-	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/gomatrixserverlib/spec"
 
 	"github.com/matrix-org/dendrite/internal"
@@ -72,7 +71,7 @@ func (r *Inputer) updateMemberships(
 		if change.addedEventNID != 0 {
 			ae, _ = helpers.EventMap(events).Lookup(change.addedEventNID)
 		}
-		if updates, err = r.updateMembership(updater, targetUserNID, re, ae, updates); err != nil {
+		if updates, err = r.updateMembership(ctx, updater, targetUserNID, re, ae, updates); err != nil {
 			return nil, err
 		}
 	}
@@ -80,6 +79,7 @@ func (r *Inputer) updateMemberships(
 }
 
 func (r *Inputer) updateMembership(
+	ctx context.Context,
 	updater *shared.RoomUpdater,
 	targetUserNID types.EventStateKeyNID,
 	remove, add *types.Event,
@@ -97,7 +97,7 @@ func (r *Inputer) updateMembership(
 
 	var targetLocal bool
 	if add != nil {
-		targetLocal = r.isLocalTarget(add)
+		targetLocal = r.isLocalTarget(ctx, add)
 	}
 
 	mu, err := updater.MembershipUpdater(targetUserNID, targetLocal)
@@ -136,11 +136,14 @@ func (r *Inputer) updateMembership(
 	}
 }
 
-func (r *Inputer) isLocalTarget(event *types.Event) bool {
+func (r *Inputer) isLocalTarget(ctx context.Context, event *types.Event) bool {
 	isTargetLocalUser := false
 	if statekey := event.StateKey(); statekey != nil {
-		_, domain, _ := gomatrixserverlib.SplitID('@', *statekey)
-		isTargetLocalUser = domain == r.ServerName
+		userID, err := r.Queryer.QueryUserIDForSender(ctx, event.RoomID(), spec.SenderID(*statekey))
+		if err != nil || userID == nil {
+			return isTargetLocalUser
+		}
+		isTargetLocalUser = userID.Domain() == r.ServerName
 	}
 	return isTargetLocalUser
 }