diff --git a/src/include/lwip/sys.h b/src/include/lwip/sys.h
index fc666ca8..04fde7a7 100644
--- a/src/include/lwip/sys.h
+++ b/src/include/lwip/sys.h
@@ -65,8 +65,6 @@ struct sys_timeo {u8_t dummy;};
 
 #else /* NO_SYS */
 
-#include "arch/sys_arch.h"
-
 /** Return code for timeouts from sys_arch_mbox_fetch and sys_arch_sem_wait */
 #define SYS_ARCH_TIMEOUT 0xffffffffUL
 
@@ -75,6 +73,8 @@ struct sys_timeo {u8_t dummy;};
  */
 #define SYS_MBOX_EMPTY SYS_ARCH_TIMEOUT 
 
+#include "arch/sys_arch.h"
+
 typedef void (* sys_timeout_handler)(void *arg);
 
 struct sys_timeo {