diff --git a/ref/blake2xs-ref.c b/ref/blake2xs-ref.c
index e7a89f8..4261e7a 100644
--- a/ref/blake2xs-ref.c
+++ b/ref/blake2xs-ref.c
@@ -33,7 +33,7 @@ int blake2xs_init_key( blake2xs_state *S, const size_t outlen, const void *key,
     return -1;
   }
 
-  if (NULL != key && keylen > BLAKE2B_KEYBYTES) {
+  if (NULL != key && keylen > BLAKE2S_KEYBYTES) {
     return -1;
   }