Fixes #28549

Change-Id: Iba71bb2edd0759004e0c7df92b2b8f1197bd62d3
Reviewed-on: https://go-review.googlesource.com/c/146901
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>