diff --git pthread/knot_comb.c pthread/knot_comb.c
index ad59515..1a65063 100644
--- pthread/knot_comb.c
+++ pthread/knot_comb.c
@@ -1106,7 +1106,7 @@ void accept_loop(int id , int s )
       if (! attr_init_done) {
         pthread_attr_init(& attr);
         rv = pthread_attr_setdetachstate(& attr, 1);
-        if (! (rv == 0)) {
+        if (rv != 0) {
           assert_failed((char *)"knot.c", 472U, "accept_loop", (char *)"rv == 0");
         }
         attr_init_done = 1;