Fixes #18584

Change-Id: I5f9428758999cacee49f3449e596e0a88bc06f91
Reviewed-on: https://go-review.googlesource.com/67150
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>