diff --git a/roomserver/api/api_trace.go b/roomserver/api/api_trace.go
index 81b0dc2dc..b23263d17 100644
--- a/roomserver/api/api_trace.go
+++ b/roomserver/api/api_trace.go
@@ -20,7 +20,9 @@ type RoomserverInternalAPITrace struct {
 }
 
 func (t *RoomserverInternalAPITrace) QueryLeftUsers(ctx context.Context, req *QueryLeftUsersRequest, res *QueryLeftUsersResponse) error {
-	return t.Impl.QueryLeftUsers(ctx, req, res)
+	err := t.Impl.QueryLeftUsers(ctx, req, res)
+	util.GetLogger(ctx).WithError(err).Infof("QueryLeftUsers req=%+v res=%+v", js(req), js(res))
+	return err
 }
 
 func (t *RoomserverInternalAPITrace) SetFederationAPI(fsAPI fsAPI.RoomserverFederationAPI, keyRing *gomatrixserverlib.KeyRing) {
diff --git a/roomserver/roomserver_test.go b/roomserver/roomserver_test.go
index 4e58d14cf..518bb3722 100644
--- a/roomserver/roomserver_test.go
+++ b/roomserver/roomserver_test.go
@@ -133,6 +133,9 @@ func Test_QueryLeftUsers(t *testing.T) {
 		})
 		t.Run("Monolith", func(t *testing.T) {
 			testCase(rsAPI)
+			// also test tracing
+			traceAPI := &api.RoomserverInternalAPITrace{Impl: rsAPI}
+			testCase(traceAPI)
 		})
 
 	})