diff --git a/gtk/gtkexpander.c b/gtk/gtkexpander.c
index bc6b90e425..1eee8db992 100644
--- a/gtk/gtkexpander.c
+++ b/gtk/gtkexpander.c
@@ -1215,7 +1215,7 @@ gtk_expander_get_preferred_height_for_width (GtkWidget *widget,
 
 /**
  * gtk_expander_new:
- * @label: the text of the label
+ * @label: (nullable): the text of the label
  *
  * Creates a new expander using @label as the text of the label.
  *