diff --git a/test/sigchld.go b/test/sigchld.go
index a60d28deaa..38437e5522 100644
--- a/test/sigchld.go
+++ b/test/sigchld.go
@@ -1,4 +1,4 @@
-// +build !windows
+// +build !plan9,!windows
 // cmpout
 
 // Copyright 2009 The Go Authors. All rights reserved.