diff --git a/gobject/gbinding.c b/gobject/gbinding.c
index f92fad826..899dc84fd 100644
--- a/gobject/gbinding.c
+++ b/gobject/gbinding.c
@@ -781,8 +781,8 @@ g_binding_unbind (GBinding *binding)
  *     from the @target to the @source, or %NULL to use the default
  * @user_data: custom data to be passed to the transformation functions,
  *     or %NULL
- * @notify: function to be called when disposing the binding, to free the
- *     resources used by the transformation functions
+ * @notify: (nullable): a function to call when disposing the binding, to free
+ *     resources used by the transformation functions, or %NULL if not required
  *
  * Complete version of g_object_bind_property().
  *