Fixes golang/go#30275

Change-Id: I0636326dc5d2b59d0dbdc446c2a424c50a395b2f
Reviewed-on: https://go-review.googlesource.com/c/162923Reviewed-by: Mikio Hara <mikioh.public.networking@gmail.com>
Run-TryBot: Mikio Hara <mikioh.public.networking@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>