Fixes #14570.

Change-Id: Ief84a14585bfc209e38cdf15702c2f54ba759714
Reviewed-on: https://go-review.googlesource.com/20057
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>