Fixes #19891

Change-Id: I2f2684dd5fbfcf93fca0f2c3caf678f44605687f
Reviewed-on: https://go-review.googlesource.com/40090Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>