Fixes #14270.

Change-Id: Iaf2496a24b1aba443391b90951cef472add73f13
Reviewed-on: https://go-review.googlesource.com/45950
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>