Fixes #17276

Change-Id: I0188cf9bc5fdb48c71ad929cc54206d03e0b96e4
Reviewed-on: https://go-review.googlesource.com/29995Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>