Fixes #16648

Change-Id: I3ab21ab33ca3f41219de9518ac6a39f49131e5e5
Reviewed-on: https://go-review.googlesource.com/26692Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>