This picks up just a trivial fix,
making vet (and thus me) happy.

Change-Id: Ib82ae44c081ff1ec5c078196a6cd5e1a3505d03b
Reviewed-on: https://go-review.googlesource.com/32427
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>