Fixes #15079

Change-Id: Ib4dd9eab322da39234008e040100e75cb58761b3
Reviewed-on: https://go-review.googlesource.com/21501Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>