Fixes #16722

Change-Id: I50a0e69d3e79d13bc1860cd983267c3db087a4b8
Reviewed-on: https://go-review.googlesource.com/27119Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-on: https://go-review.googlesource.com/28630