Fixes #18054

Change-Id: I6773943a95b92eebd7e347f8f7a80843b4827243
Reviewed-on: https://go-review.googlesource.com/33630Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>