Add call to mbedtls_x509_crt_free()

diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index c9517e3..78637ba 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -12057,6 +12057,7 @@
 #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
 
 #if defined(MBEDTLS_SSL_FREE_SERVER_CERTIFICATE)
+    mbedtls_x509_crt_free( ssl->session_negotiate->peer_cert );
     mbedtls_free( ssl->session->peer_cert );
     ssl->session->peer_cert = NULL;
 #endif /* MBEDTLS_SSL_FREE_SERVER_CERTIFICATE */