diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 30c3c3a..f55dede 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -1336,6 +1336,9 @@
 void mbedtls_ssl_optimize_checksum( mbedtls_ssl_context *ssl,
                             const mbedtls_ssl_ciphersuite_t *ciphersuite_info );
 
+void mbedtls_ssl_add_hs_hdr_to_checksum( mbedtls_ssl_context *ssl,
+                                         unsigned hs_type,
+                                         size_t total_hs_len );
 /*
  * Update checksum of handshake messages.
  */