diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index afe7e9224e8b6d8e20e2b94df9ff93280b3df572..18816ac5bfa006cc8988c2575d0b3fa4de7cd174 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -11345,8 +11345,7 @@ gtk_widget_activate_action_variant (GtkWidget  *widget,
  * gtk_widget_activate_action:
  * @widget: a `GtkWidget`
  * @name: the name of the action to activate
- * @format_string: GVariant format string for arguments or %NULL
- *   for no arguments
+ * @format_string: (nullable): GVariant format string for arguments
  * @...: arguments, as given by format string
  *
  * Looks up the action in the action groups associated