Fixes #14498.

Change-Id: I4cfab3e45898466179cefbd31c6f7f796da82363
Reviewed-on: https://go-review.googlesource.com/19874Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>