Fixes golang/go#19821

Change-Id: Iee5d43dfeaaf580c39ca38a7a3a74cf2a8b347b3
Reviewed-on: https://go-review.googlesource.com/44381
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Nigel Tao <nigeltao@golang.org>