diff --git a/ipv6/genericopt_stub.go b/ipv6/genericopt_stub.go
index 1f8df1b..8871df9 100644
--- a/ipv6/genericopt_stub.go
+++ b/ipv6/genericopt_stub.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build plan9 solaris
+// +build nacl plan9 solaris
 
 package ipv6