Fixes #23653.

Change-Id: Ic1e3c8f156ae576cfb5da1b4d082d4b12fae114f
Reviewed-on: https://go-review.googlesource.com/91317
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>