diff --git a/mcapi/crypto.h b/mcapi/crypto.h
index 3a6a87a6f..6db1dd211 100644
--- a/mcapi/crypto.h
+++ b/mcapi/crypto.h
@@ -104,7 +104,7 @@ enum {
 
 /* HMAC */
 typedef struct CRYPT_HMAC_CTX {
-    long long holder[68];   /* big enough to hold internal, but check on init */
+    long long holder[69];   /* big enough to hold internal, but check on init */
 } CRYPT_HMAC_CTX;
 
 int CRYPT_HMAC_SetKey(CRYPT_HMAC_CTX*, int, const unsigned char*, unsigned int);