Fixes #12078

Change-Id: Ia8738123b07ca29be4a0cf400ee143729c8b5b3c
Reviewed-on: https://go-review.googlesource.com/16860Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>