diff --git a/src/post_modules/GTK/pgtk.h b/src/post_modules/GTK/pgtk.h
index f72afdf2c10e790665179d20a4f4833f55f3abb4..8b2e90dd96af5a3e3592d7c0616e4a2f95125c4c 100644
--- a/src/post_modules/GTK/pgtk.h
+++ b/src/post_modules/GTK/pgtk.h
@@ -118,6 +118,10 @@ void push_pgdkobject(void *obj, struct program *def);
 GdkImage *gdkimage_from_pikeimage(struct object *img, int fast, GdkImage *i );
 struct object *pikeimage_from_gdkimage( GdkImage *img );
 
+#ifdef THIS
+#undef THIS
+#endif
+
 #define THIS ((struct object_wrapper *)Pike_fp->current_storage)
 #define THISO ((struct object_wrapper *)Pike_fp->current_storage)->obj