Fixes #18026

Change-Id: Id510f427ceffb2441c3d6f5bb5c93244e46c6497
Reviewed-on: https://go-review.googlesource.com/33477
TryBot-Result: Gobot Gobot <gobot@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>