See #10248 for details.

Fixes #10248.

Change-Id: I373545b2dca5d1da1c7149eb0a8f6c6dd8071a4c
Reviewed-on: https://go-review.googlesource.com/10503Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>