diff --git a/src_features/signMessageEIP712/eip712.h b/src_features/signMessageEIP712/eip712.h
index 6d51647..b25790f 100644
--- a/src_features/signMessageEIP712/eip712.h
+++ b/src_features/signMessageEIP712/eip712.h
@@ -59,6 +59,8 @@ typedef enum
 
 #define KECCAK256_HASH_LENGTH   32
 
+#define ARRAY_SIZE(a)   (sizeof(a) / sizeof(a[0]))
+
 typedef struct
 {
     uint16_t    length;