diff --git a/src/include/lwip/sio.h b/src/include/lwip/sio.h
index 09cf799a..7643e195 100644
--- a/src/include/lwip/sio.h
+++ b/src/include/lwip/sio.h
@@ -36,6 +36,7 @@
 #define SIO_H
 
 #include "lwip/arch.h"
+#include "lwip/opt.h"
 
 #ifdef __cplusplus
 extern "C" {