diff --git a/src/core/timers.c b/src/core/timers.c
index 23f8296b..94e8029a 100644
--- a/src/core/timers.c
+++ b/src/core/timers.c
@@ -326,7 +326,9 @@ sys_timeout(u32_t msecs, sys_timeout_handler handler, void *arg)
 #endif /* LWIP_DEBUG_TIMERNAMES */
 {
   struct sys_timeo *timeout, *t;
+#if NO_SYS
   u32_t now, diff;
+#endif
 
   timeout = (struct sys_timeo *)memp_malloc(MEMP_SYS_TIMEOUT);
   if (timeout == NULL) {
@@ -334,6 +336,7 @@ sys_timeout(u32_t msecs, sys_timeout_handler handler, void *arg)
     return;
   }
 
+#if NO_SYS
   now = sys_now();
   if (next_timeout == NULL) {
     diff = 0;
@@ -341,11 +344,16 @@ sys_timeout(u32_t msecs, sys_timeout_handler handler, void *arg)
   } else {
     diff = now - timeouts_last_time;
   }
+#endif
 
   timeout->next = NULL;
   timeout->h = handler;
   timeout->arg = arg;
+#if NO_SYS
   timeout->time = msecs + diff;
+#else
+  timeout->time = msecs;
+#endif
 #if LWIP_DEBUG_TIMERNAMES
   timeout->handler_name = handler_name;
   LWIP_DEBUGF(TIMERS_DEBUG, ("sys_timeout: %p msecs=%"U32_F" handler=%s arg=%p\n",