diff --git a/unix/flock.go b/unix/flock.go
index ce67a595..2994ce75 100644
--- a/unix/flock.go
+++ b/unix/flock.go
@@ -1,5 +1,3 @@
-// +build linux darwin freebsd openbsd netbsd dragonfly
-
 // Copyright 2014 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.