Fixes #20348

Change-Id: I831aeeee8e20d55b3e47dea67786e883b213cd58
Reviewed-on: https://go-review.googlesource.com/106457
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Aram Hăvărneanu <aram@mgk.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>