Fixes golang/go#8760

Change-Id: Iacb5802ce6256fc5fb61b558f2d0bc0dcf593c96
Reviewed-on: https://go-review.googlesource.com/103355
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>