Followup to CL 39152.

Change-Id: I9bfed0c6071ea3d3a43294a6c4a50edc131368cf
Reviewed-on: https://go-review.googlesource.com/39313
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>