diff --git a/ports/unix/port/sys_arch.c b/ports/unix/port/sys_arch.c
index 3404e8d..fa5bd3c 100644
--- a/ports/unix/port/sys_arch.c
+++ b/ports/unix/port/sys_arch.c
@@ -606,13 +606,27 @@ sys_mutex_free(struct sys_mutex **mutex)
 
 /*-----------------------------------------------------------------------------------*/
 /* Time */
+
+#if defined FUZZED_TMR
+extern u32_t total_external_delay;
+#endif
+
 u32_t
 sys_now(void)
 {
   struct timespec ts;
+  u32_t now;
 
   get_monotonic_time(&ts);
-  return (u32_t)(ts.tv_sec * 1000L + ts.tv_nsec / 1000000L);
+#if defined FUZZED_TMR
+  now = ((u32_t)(ts.tv_sec * 1000L + ts.tv_nsec / 1000000L) + total_external_delay);
+  LWIP_DEBUGF(SYS_DEBUG, ("sys_now: total_external_delay = %u\n", total_external_delay));
+  LWIP_DEBUGF(SYS_DEBUG, ("sys_now: now = %u\n", now));
+  return now;
+#else
+  now = (u32_t)(ts.tv_sec * 1000L + ts.tv_nsec / 1000000L);
+  return now;
+#endif
 }
 
 u32_t