diff --git a/gio/gsocketaddress.c b/gio/gsocketaddress.c
index 0a7d9eb50..defd965e0 100644
--- a/gio/gsocketaddress.c
+++ b/gio/gsocketaddress.c
@@ -147,7 +147,8 @@ g_socket_address_init (GSocketAddress *address)
  * g_socket_address_to_native().
  *
  * Returns: the size of the native struct sockaddr that
- *     @address represents
+ *     @address represents, or `-1` if @address
+ *     is not valid
  *
  * Since: 2.22
  */