diff --git a/ssl/tls13_server.c b/ssl/tls13_server.c
index 4cfd265..53e5363 100644
--- a/ssl/tls13_server.c
+++ b/ssl/tls13_server.c
@@ -88,7 +88,7 @@
   int found_key_share;
   uint8_t *dhe_secret;
   size_t dhe_secret_len;
-  uint8_t alert;
+  uint8_t alert = SSL_AD_DECODE_ERROR;
   if (!ssl_ext_key_share_parse_clienthello(ssl, &found_key_share, &dhe_secret,
                                            &dhe_secret_len, &alert,
                                            &key_share)) {