Fixes #12301

Change-Id: I8d01ec9551c6cff7e6129e06a7deb36a3be9de41
Reviewed-on: https://go-review.googlesource.com/16751Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>