diff --git a/gobject/gclosure.c b/gobject/gclosure.c
index 6d41e6d8a..364f4aab1 100644
--- a/gobject/gclosure.c
+++ b/gobject/gclosure.c
@@ -761,7 +761,7 @@ g_closure_remove_finalize_notifier (GClosure      *closure,
 /**
  * g_closure_invoke:
  * @closure: a #GClosure
- * @return_value: (optional) (out): a #GValue to store the return
+ * @return_value: (optional) (inout): a #GValue to store the return
  *                value. May be %NULL if the callback of @closure
  *                doesn't return a value.
  * @n_param_values: the length of the @param_values array