diff --git a/gmtls/gm_handshake_client_double.go b/gmtls/gm_handshake_client_double.go
index a395ff1d..9bb3fc7c 100644
--- a/gmtls/gm_handshake_client_double.go
+++ b/gmtls/gm_handshake_client_double.go
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !single_cert
+
 package gmtls
 
 import (