Fixes #17755

Change-Id: I1ad1edc382b1312d992963054eb82648cb5112d2
Reviewed-on: https://go-review.googlesource.com/32588
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>