diff --git a/library/ssl_tls12_server.c b/library/ssl_tls12_server.c
index 03ef8fd5f9..2a825e07b1 100644
--- a/library/ssl_tls12_server.c
+++ b/library/ssl_tls12_server.c
@@ -2175,6 +2175,7 @@ static int ssl_write_server_hello(mbedtls_ssl_context *ssl)
         MBEDTLS_SSL_DEBUG_RET(1, "ssl_write_ecjpake_kkpp_ext", ret);
         return ret;
     }
+    ext_len += olen;
 #endif
 
 #if defined(MBEDTLS_SSL_ALPN)