Fixes #8434

Change-Id: I323222b4160f3aba35cac1de7f6df93c524b72ec
Reviewed-on: https://go-review.googlesource.com/14169Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>