Fixes #9871 for Go 1.4.

Change-Id: I550a5bdb29e9a872652e0dd468a434227d7d9502
Reviewed-on: https://go-review.googlesource.com/4937
Run-TryBot: Minux Ma <minux@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Andrew Gerrand <adg@golang.org>