diff --git a/ref/blake2.h b/ref/blake2.h
index cef9bf2..9e1a154 100644
--- a/ref/blake2.h
+++ b/ref/blake2.h
@@ -152,6 +152,14 @@ extern "C" {
   int blake2bp_update( blake2bp_state *S, const void *in, size_t inlen );
   int blake2bp_final( blake2bp_state *S, void *out, size_t outlen );
 
+int blake2xs_init( blake2xs_state *S, const size_t outlen, const void *key, size_t keylen );
+int blake2xs_update( blake2xs_state *S, const void *in, size_t inlen );
+int blake2xs_final(blake2xs_state *S, void *out, size_t outlen);
+
+int blake2xb_init( blake2xs_state *S, const size_t outlen, const void *key, size_t keylen );
+int blake2xb_update( blake2xs_state *S, const void *in, size_t inlen );
+int blake2xb_final(blake2xs_state *S, void *out, size_t outlen);
+
   /* Simple API */
   int blake2s( void *out, size_t outlen, const void *in, size_t inlen, const void *key, size_t keylen );
   int blake2b( void *out, size_t outlen, const void *in, size_t inlen, const void *key, size_t keylen );