Index: uspace/lib/c/generic/async.c
===================================================================
--- uspace/lib/c/generic/async.c	(revision 0e1edf19537c83d89c364a0927385558456e9464)
+++ uspace/lib/c/generic/async.c	(revision b2fa2d86f31fd2f3a0ce7dad1f5039f5efa891f1)
@@ -2068,4 +2068,5 @@
 	
 	async_sess_t *sess = exch->sess;
+	assert(sess != NULL);
 	
 	atomic_dec(&sess->refcnt);