diff --git a/gdk/mir/gdkmirwindowimpl.c b/gdk/mir/gdkmirwindowimpl.c
index 16035a02a4..25e57c6a1e 100644
--- a/gdk/mir/gdkmirwindowimpl.c
+++ b/gdk/mir/gdkmirwindowimpl.c
@@ -871,8 +871,6 @@ gdk_mir_window_impl_set_transient_for (GdkWindow *window,
   if (impl->transient_for == parent)
     return;
 
-  g_return_if_fail (impl->transient_for == NULL);
-
   /* Link this window to the parent */
   impl->transient_for = parent;
 }