Fixes #14262.

Change-Id: Id590995dd4460e81f6b91bcfb3f02515a97650fe
Reviewed-on: https://go-review.googlesource.com/19361
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>