diff --git a/widget/gtk/GRefPtr.h b/widget/gtk/GRefPtr.h
--- a/widget/gtk/GRefPtr.h
+++ b/widget/gtk/GRefPtr.h
@@ -48,10 +48,11 @@
 GOBJECT_TRAITS(GCancellable)
 GOBJECT_TRAITS(GtkIMContext)
 GOBJECT_TRAITS(GUnixFDList)
 GOBJECT_TRAITS(GtkCssProvider)
 GOBJECT_TRAITS(GDBusMethodInvocation)
+GOBJECT_TRAITS(GdkWindow)
 
 #undef GOBJECT_TRAITS
 
 template <>
 struct RefPtrTraits<GVariant> {