Fixes #28772

Change-Id: I9446d95fb73fbcbb1cd9a4d2156ebc91bc9e91cb
Reviewed-on: https://go-review.googlesource.com/c/149858
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>