--- mtr-0.72/net.c
+++ mtr-0.72/net.c
@@ -355,7 +355,7 @@ void net_process_ping(int seq, void * addr, struct timeval now)
 
   totusec = (now.tv_sec  - sequence[seq].time.tv_sec ) * 1000000 +
             (now.tv_usec - sequence[seq].time.tv_usec);
-  /* impossible? if( totusec < 0 ) totusec = 0 */;
+  if (totusec < 0) totusec = 0;
 
   if ( addrcmp( (void *) &(host[index].addr),
 		(void *) &unspec_addr, af ) == 0 ) {