diff --git a/util/fds.go b/util/fds.go
index 58ca42a..57d490d 100644
--- a/util/fds.go
+++ b/util/fds.go
@@ -1,3 +1,5 @@
+// +build !windows,!darwin
+
 package util
 
 import (
diff --git a/util/prctl.go b/util/prctl.go
index cefa250..1c782e8 100644
--- a/util/prctl.go
+++ b/util/prctl.go
@@ -1,4 +1,4 @@
-// + build linux
+// +build linux
 
 // http://man7.org/linux/man-pages/man2/prctl.2.html
 package util