diff --git a/src/net/empty.s b/src/net/empty.s
index a515c2fe29..f0b255a0cf 100644
--- a/src/net/empty.s
+++ b/src/net/empty.s
@@ -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 !cgo
+
 // This file is required to prevent compiler errors
 // when the package built with CGO_ENABLED=0.
 // Otherwise the compiler says: