The problem with parents and child in uGUI

I need a Dialog for the game,but there is a problem about render order between Parent and Child in uGUI

Canvas
-Label
–Bg

As this situation,there are two component for the Dialog.

The -Label will resize itself by the amount of text , and the --Bg will also resize itself by the size of the -Label. (set by Rect Transform)

But the --Bg is always in front of the -Label , I only can see the --Bg without any text.

Is there any solution without change the sorting,and the text will be in front of the --Bg?

Add a component “Canvas” to the child, check “Override sorting” and set a sorting order that is lower than the canvas of the parent.

see also: https://twitter.com/imi_scholz/status/722417087910649856