Fixes #13073

Change-Id: I4fd9c6c61f1b9d49f66816839ca35209b4147ae3
Reviewed-on: https://go-review.googlesource.com/17167Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-on: https://go-review.googlesource.com/17168Reviewed-by: Andrew Gerrand <adg@golang.org>