Fixes #18086

Change-Id: Idc501dd37893e04a01c6ed9920147d24c0c1fa18
Reviewed-on: https://go-review.googlesource.com/34202Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>