Fixes #21414

Change-Id: Idff6e269ae32b33253067c9f32cac25256eb7f1c
Reviewed-on: https://go-review.googlesource.com/55251Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>