Index: uspace/lib/c/generic/async.c
===================================================================
--- uspace/lib/c/generic/async.c	(revision 0e1edf19537c83d89c364a0927385558456e9464)
+++ uspace/lib/c/generic/async.c	(revision 6b0b5085f6bc7e20d2ccf94b45b70e6c4d5262df)
@@ -2068,4 +2068,5 @@
 	
 	async_sess_t *sess = exch->sess;
+	assert(sess != NULL);
 	
 	atomic_dec(&sess->refcnt);