Fixes #17938

Change-Id: Iad12155f4976846bd4a9a53869f89e40e5b3deb3
Reviewed-on: https://go-review.googlesource.com/34147
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>