Fixes #16903.

Change-Id: I1f6fcd57e14b2b62e208b7bb3adccd5fd7f8bdbc
Reviewed-on: https://go-review.googlesource.com/27933
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>