diff --git a/gtk/gtklistbase.c b/gtk/gtklistbase.c
index ed4f84ad2a..5bc7ecaee3 100644
--- a/gtk/gtklistbase.c
+++ b/gtk/gtklistbase.c
@@ -1148,7 +1148,7 @@ gtk_list_base_class_init (GtkListBaseClass *klass)
                        P_("The orientation of the orientable"),
                        GTK_TYPE_ORIENTATION,
                        GTK_ORIENTATION_VERTICAL,
-                       G_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY | G_PARAM_EXPLICIT_NOTIFY);
+                       G_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY);
 
   g_object_class_install_properties (gobject_class, N_PROPS, properties);