Fixes #15745.

Change-Id: I6f9a1dcf0b1d97cb443900c7d8da09ead83d4b6a
Reviewed-on: https://go-review.googlesource.com/23243
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>