diff --git a/lib/hmac.h b/lib/hmac.h
index 04018fdb..3aaded37 100644
--- a/lib/hmac.h
+++ b/lib/hmac.h
@@ -33,6 +33,8 @@
 
 #include "digest.h"
 
+void hmac_md5(const char *msg, const unsigned int msg_len,
+        unsigned char *hmac, const char *hmac_key, const int hmac_key_len);
 void hmac_sha1(const char *msg, const unsigned int msg_len,
         unsigned char *hmac, const char *hmac_key, const int hmac_key_len);
 void hmac_sha256(const char *msg, const unsigned int msg_len,