Fixes golang/go#17107

Change-Id: Ibc18c6595ab6482a2feacaf51b93516fbc7cb2d6
Reviewed-on: https://go-review.googlesource.com/29166
Run-TryBot: Shawn Walker-Salas <shawn.walker@oracle.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>