diff --git a/src/core/init.c b/src/core/init.c
index b78384f9..400e2e5e 100644
--- a/src/core/init.c
+++ b/src/core/init.c
@@ -252,7 +252,7 @@
 #ifdef ETHARP_ALWAYS_INSERT
   #error "ETHARP_ALWAYS_INSERT option is deprecated. Remove it from your lwipopts.h."
 #endif
-#if LWIP_TCPIP_CORE_LOCKING && LWIP_COMPAT_MUTEX && !defined(LWIP_COMPAT_MUTEX_ALLOWED)
+#if !NO_SYS && LWIP_TCPIP_CORE_LOCKING && LWIP_COMPAT_MUTEX && !defined(LWIP_COMPAT_MUTEX_ALLOWED)
   #error "LWIP_COMPAT_MUTEX cannot prevent priority inversion. It is recommended to implement priority-aware mutexes. (Define LWIP_COMPAT_MUTEX_ALLOWED to disable this error.)"
 #endif