diff --git a/gdbus/client.c b/gdbus/client.c
index 55f1d89..a21b66a 100644
--- a/gdbus/client.c
+++ b/gdbus/client.c
@@ -1119,6 +1119,8 @@ static DBusHandlerResult message_filter(DBusConnection *connection,
 		return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
 
 	sender = dbus_message_get_sender(message);
+	if (sender == NULL)
+		return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
 
 	if (g_str_equal(sender, DBUS_SERVICE_DBUS) == TRUE) {
 		const char *interface, *member;