Index: head/sys/kern/uipc_usrreq.c
===================================================================
--- head/sys/kern/uipc_usrreq.c
+++ head/sys/kern/uipc_usrreq.c
@@ -736,8 +736,10 @@
 
 	UNP_PCB_LOCK(unp);
 	if (unp->unp_vnode == NULL) {
+		/* Already connected or not bound to an address. */
+		error = unp->unp_conn != NULL ? EINVAL : EDESTADDRREQ;
 		UNP_PCB_UNLOCK(unp);
-		return (EINVAL);
+		return (error);
 	}
 
 	SOCK_LOCK(so);