Fixes #12002.

Change-Id: I7262f4520560ac158fc2ee3ce1d2f7a488d40354
Reviewed-on: https://go-review.googlesource.com/16666


Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>