diff --git a/gtk/gtkobject.h b/gtk/gtkobject.h
index f8ec563031..c927f5bf5b 100644
--- a/gtk/gtkobject.h
+++ b/gtk/gtkobject.h
@@ -32,6 +32,7 @@
 #define __GTK_OBJECT_H__
 
 
+#include <gdk/gdkconfig.h>
 #include <gtk/gtkenums.h>
 #include <gtk/gtktypeutils.h>
 #include <gtk/gtkdebug.h>
@@ -93,7 +94,7 @@ struct _GtkObject
    *  aligned on 4 or 8 byte boundaries. If a new bitfield were
    *  used in GtkWidget much space would be wasted.
    */
-  guint32 flags;
+  guint32 GSEAL (flags);
 };
 
 struct _GtkObjectClass