Fixes #16121.

Change-Id: I7b838fb6fb9f098e6c348d67379fdc81fb0d69a4
Reviewed-on: https://go-review.googlesource.com/24270
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>