diff --git a/gdk/gdkwindow.c b/gdk/gdkwindow.c
index 654e732b3b..c550aeaaf1 100644
--- a/gdk/gdkwindow.c
+++ b/gdk/gdkwindow.c
@@ -5139,7 +5139,8 @@ gdk_window_ref_cairo_surface (GdkDrawable *drawable)
 	  int width, height;
 	  GdkDrawable *source;
 
-          gdk_drawable_get_size (private->impl_window, &width, &height);
+          gdk_drawable_get_size ((GdkWindow *) private->impl_window,
+                                 &width, &height);
 
 	  source = _gdk_drawable_get_source_drawable (drawable);