diff --git a/ssh/test/forward_unix_test.go b/ssh/test/forward_unix_test.go
index 881a9da..3a57c10 100644
--- a/ssh/test/forward_unix_test.go
+++ b/ssh/test/forward_unix_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd
+// +build darwin freebsd linux netbsd openbsd plan9
 
 package test
 
diff --git a/ssh/test/test_unix_test.go b/ssh/test/test_unix_test.go
index e56fcaf..86df3f4 100644
--- a/ssh/test/test_unix_test.go
+++ b/ssh/test/test_unix_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd
+// +build darwin freebsd linux netbsd openbsd plan9
 
 package test