Fixes #14387.

Change-Id: Icc98be80f549c5e1f55c5e693bfea97b456a6c41
Reviewed-on: https://go-review.googlesource.com/19621
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-on: https://go-review.googlesource.com/22036Reviewed-by: Ian Lance Taylor <iant@golang.org>