Fixes #29383

Change-Id: I0fb2929863e153b96d32d851e25e536231e4ae65
Reviewed-on: https://go-review.googlesource.com/c/155638
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>