diff --git a/unix/export_test.go b/unix/export_test.go
index 570aa7ac..b4fdd970 100644
--- a/unix/export_test.go
+++ b/unix/export_test.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 darwin dragonfly freebsd linux netbsd openbsd solaris
+
 package unix
 
 var Itoa = itoa