Initially added in https://golang.org/cl/9842 and
subsequently broken in https://golang.org/cl/85756.

Fixes golang/go#23361

Change-Id: Id458efdb4a9ffc5f038b4070fd514de9f78c17d7
Reviewed-on: https://go-review.googlesource.com/86755Reviewed-by: Ian Lance Taylor <iant@golang.org>