don't change the default behavior
diff --git a/lib/openssl.c b/lib/openssl.c
index 2d077cc..3ce0397 100644
--- a/lib/openssl.c
+++ b/lib/openssl.c
@@ -1237,7 +1237,6 @@
         }
         X509_VERIFY_PARAM_set_purpose(params, is_server ? X509_PURPOSE_SSL_SERVER : X509_PURPOSE_SSL_CLIENT);
         X509_VERIFY_PARAM_set_depth(params, 98); /* use the default of OpenSSL 1.0.2 and above; see `man SSL_CTX_set_verify` */
-        X509_VERIFY_PARAM_set_flags(params, X509_V_FLAG_PARTIAL_CHAIN);
         if (!is_server) {
             assert(server_name != NULL && "ptls_set_server_name MUST be called");
             if (server_name != NULL) {