Fixes #21887

Change-Id: I30e8e03ecfb67a2c4deedc2c8436da4c4782136d
Reviewed-on: https://go-review.googlesource.com/63971
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>