Fixes #14981

Change-Id: I39b906d119ca96815801a0fbef2dbe524a3246ff
Reviewed-on: https://go-review.googlesource.com/23009Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>