diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index bb51575..7d5f95c 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -4892,7 +4892,7 @@
  * Point 2 is needed when the peer is resending, and we have already received
  * the first record from a datagram but are still waiting for the others.
  */
-static int ssl_parse_record_header( mbedtls_ssl_context *ssl,
+static int ssl_parse_record_header( mbedtls_ssl_context const *ssl,
                                     unsigned char *buf,
                                     size_t len,
                                     mbedtls_record *rec )