Fixes #17415

Change-Id: I6f896d549092e5e0dba72351e5385992b4cbe90f
Reviewed-on: https://go-review.googlesource.com/30933
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>