diff --git a/collects/mred/private/wx/gtk/types.rkt b/collects/mred/private/wx/gtk/types.rkt
index 0dc4d8c1fe..20bb567ccd 100644
--- a/collects/mred/private/wx/gtk/types.rkt
+++ b/collects/mred/private/wx/gtk/types.rkt
@@ -54,7 +54,7 @@
 (define _gfloat _float)
 (define _GdkEventType _int)
 
-(define _GdkAtom _long)
+(define _GdkAtom _intptr)
 
 (define-cstruct _GdkEventButton ([type _GdkEventType]
                                  [window _GdkWindow]