Fixes #19329.

Change-Id: I6d8bb112a56d751a6d3ea9bd6021803cb9f59234
Reviewed-on: https://go-review.googlesource.com/37619Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>