Caught by vet.

Updates #11041

Change-Id: I4dbb2eeaf633eea5976074840064edc2349e01d8
Reviewed-on: https://go-review.googlesource.com/27120
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: David Crawshaw <crawshaw@golang.org>