diff --git a/lib/system/freertos/sys.h b/lib/system/freertos/sys.h
index 6e6d0be6..34b3617f 100644
--- a/lib/system/freertos/sys.h
+++ b/lib/system/freertos/sys.h
@@ -16,6 +16,8 @@
 #ifndef __METAL_FREERTOS_SYS__H__
 #define __METAL_FREERTOS_SYS__H__
 
+#include <metal/errno.h>
+
 #include "./@PROJECT_MACHINE@/sys.h"
 
 #ifdef __cplusplus