diff --git a/gtk/gtkcontainer.h b/gtk/gtkcontainer.h
index 0cc6a2db6d..e7c2ff38bc 100644
--- a/gtk/gtkcontainer.h
+++ b/gtk/gtkcontainer.h
@@ -62,10 +62,10 @@ struct _GtkContainer
   guint GSEAL (border_width : 16);
 
   /*< private >*/
-  guint need_resize : 1;
-  guint resize_mode : 2;
-  guint reallocate_redraws : 1;
-  guint has_focus_chain : 1;
+  guint GSEAL (need_resize : 1);
+  guint GSEAL (resize_mode : 2);
+  guint GSEAL (reallocate_redraws : 1);
+  guint GSEAL (has_focus_chain : 1);
 };
 
 struct _GtkContainerClass