Fixes #19976

Change-Id: I48486467066784a9dcc24357ec94a1be85265a6f
Reviewed-on: https://go-review.googlesource.com/40940
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>