Fixes #13090

Change-Id: I5612d792dabdff89bd0cec57dc2cacf9be7ebf64
Reviewed-on: https://go-review.googlesource.com/16341
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>