diff --git a/internal/netreflect/socket.go b/internal/netreflect/socket.go
index e82e51c4..1495b65f 100644
--- a/internal/netreflect/socket.go
+++ b/internal/netreflect/socket.go
@@ -2,8 +2,12 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !go1.9
+
 // Package netreflect implements run-time reflection for the
 // facilities of net package.
+//
+// This package works only for Go 1.8 or below.
 package netreflect
 
 import (
diff --git a/internal/netreflect/socket_posix.go b/internal/netreflect/socket_posix.go
index df475a2b..410c0924 100644
--- a/internal/netreflect/socket_posix.go
+++ b/internal/netreflect/socket_posix.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !go1.9
 // +build darwin dragonfly freebsd linux netbsd openbsd solaris windows
 
 package netreflect
diff --git a/internal/netreflect/socket_stub.go b/internal/netreflect/socket_stub.go
index 85adb4b7..17b20c47 100644
--- a/internal/netreflect/socket_stub.go
+++ b/internal/netreflect/socket_stub.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !go1.9
 // +build !darwin,!dragonfly,!freebsd,!linux,!netbsd,!openbsd,!solaris,!windows
 
 package netreflect
diff --git a/internal/netreflect/socket_test.go b/internal/netreflect/socket_test.go
index fd01a9b2..b3aad0d9 100644
--- a/internal/netreflect/socket_test.go
+++ b/internal/netreflect/socket_test.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !go1.9
 // +build darwin dragonfly freebsd linux netbsd openbsd solaris windows
 
 package netreflect_test