Fixes #19270.

Change-Id: Ie7538ff8465138a8bc02572e84cf5d00de7bbdd1
Reviewed-on: https://go-review.googlesource.com/37718
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>