Fixes #14859

Change-Id: I262d634ee22498ec9855d273afdd409149765294
Reviewed-on: https://go-review.googlesource.com/21195Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>