diff --git a/arch/sandbox/include/asm/io.h b/arch/sandbox/include/asm/io.h
index 72953828f96..cd3f5d6fd40 100644
--- a/arch/sandbox/include/asm/io.h
+++ b/arch/sandbox/include/asm/io.h
@@ -14,6 +14,7 @@ static inline void sync(void)
 
 #define mb()	sync()
 #define dmb()	sync()
+#define wmb()	sync()
 
 enum sandboxio_size_t {
 	SB_SIZE_8,