Fixes #17532

Change-Id: Id62671d505c77ea924b3570a504cdc3b157e5a0d
Reviewed-on: https://go-review.googlesource.com/31734
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>