diff --git a/src/proto_uxdg.c b/src/proto_uxdg.c
index 7eb5a62..3db94f1 100644
--- a/src/proto_uxdg.c
+++ b/src/proto_uxdg.c
@@ -95,6 +95,7 @@
 
 	if (!(listener->rx.flags & RX_F_BOUND)) {
 		msg = "receiving socket not bound";
+		err |= ERR_FATAL | ERR_ALERT;
 		goto uxdg_return;
 	}