Issue introduced by https://go-review.googlesource.com/#/c/16920/ .

TBR=rsc

Change-Id: I2a0e0c81f641f869568230837c566913f6538f37
Reviewed-on: https://go-review.googlesource.com/16990
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>