Fixes #29555

Change-Id: Ia3c0dd65bcf94dea3f6e04c23c1fe5d6d0b2c1e9
Reviewed-on: https://go-review.googlesource.com/c/156399
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>