Fixes golang/go#20559

Change-Id: Ieb794badb56c6830e32028133f67223424323ea2
Reviewed-on: https://go-review.googlesource.com/44710Reviewed-by: Matt Layher <mdlayher@gmail.com>
Run-TryBot: Matt Layher <mdlayher@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>