Fixes #23759.

Change-Id: I0407ebfea507991fc205f7b04bc5798808a5c5f6
Reviewed-on: https://go-review.googlesource.com/97496Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: David Symonds <dsymonds@golang.org>