Fixes #15675

Change-Id: I8bad220988e5d690f20804db970b2db037c81187
Reviewed-on: https://go-review.googlesource.com/23086Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>