Updates #15735.
Fixes #15741.

Change-Id: Ic4ad7e948e8c3ab5feffef89d7a37417f82722a1
Reviewed-on: https://go-review.googlesource.com/23199
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>