Fixes #15948

Change-Id: Idd79859b3e98d61cd4e3ef9caa5d3b2524fd026a
Reviewed-on: https://go-review.googlesource.com/23810Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>