Fixes #14576.

Change-Id: I760907c67c97cb827cf48ba7eb0bb2f4f8d4d790
Reviewed-on: https://go-review.googlesource.com/23111
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>