Fixes #17355

Change-Id: I5390979cd0081b61a639466377faa46b4221b74a
Reviewed-on: https://go-review.googlesource.com/31329
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>