Fixes #15911.

Change-Id: I500533484de61aa09abe4cecb010445e3176324e
Reviewed-on: https://go-review.googlesource.com/26760
TryBot-Result: Gobot Gobot <gobot@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>