diff --git a/gtk/gtkicontheme.h b/gtk/gtkicontheme.h
index ec8154394c..74f6e30077 100644
--- a/gtk/gtkicontheme.h
+++ b/gtk/gtkicontheme.h
@@ -49,7 +49,7 @@ struct _GtkIconTheme
   /*< private >*/
   GObject parent_instance;
 
-  GtkIconThemePrivate *priv;
+  GtkIconThemePrivate *GSEAL (priv);
 };
 
 struct _GtkIconThemeClass