Fixes #23094.

Change-Id: I9aa36046488baa5f55cf2099e10cfb39ecd17b06
Reviewed-on: https://go-review.googlesource.com/116256
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>