diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index d16b254..381f0c4 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -1349,6 +1349,10 @@
                                          unsigned char const *msg,
                                          size_t msg_len );
 
+void mbedtls_ssl_add_hs_hdr_to_checksum( mbedtls_ssl_context *ssl,
+                                         unsigned hs_type,
+                                         size_t total_hs_len );
+
 #if defined(MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED)
 #if !defined(MBEDTLS_USE_PSA_CRYPTO)
 MBEDTLS_CHECK_RETURN_CRITICAL