Fixes #9063.

Change-Id: I536ef1f0b30c94c1ebf7922d84cb2f701b7d8a1a
Reviewed-on: https://go-review.googlesource.com/12526Reviewed-by: Adam Langley <agl@golang.org>
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>