diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 65688cf..1c359a2 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -2897,6 +2897,8 @@
 
     MBEDTLS_SSL_DEBUG_MSG(1, ("got unexpected message."));
 
+    MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_UNEXPECTED_MESSAGE,
+                                 MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE);
     return MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE;
 }