Fixes #14202

Change-Id: Ia6dccecb1b9b3f6c0838c99090e6ddf1ad43303c
Reviewed-on: https://go-review.googlesource.com/19175
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>