Fixes #17006

Change-Id: I3c2060ca5384a4b9782a7d804305d2cf4388dd5a
Reviewed-on: https://go-review.googlesource.com/29014
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>