diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index 0b10b12..f6e145b 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -173,8 +173,9 @@
      *    extension list must be kept to write
      *    the total extension list size in the end.
      */
-
+#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
     int ret;
+#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
     unsigned char* extension_start;
     size_t cur_ext_len;          /* Size of the current extension */
     size_t total_ext_len;        /* Size of list of extensions    */