Fixes #13767

Change-Id: Ib743db7d9d72022ea911bc5ac535243489425642
Reviewed-on: https://go-review.googlesource.com/18725Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>