RibbonControl: Adding control inside a RibbonTab issue

Hello All,

I am using a RibbonControl in a WPF application (.Net framework 4.5).

In which, i am trying to add a control inside the RibbonTab. But the control is getting placed at the bottom of the ribbon tab control. How to correct this behavior? Is there any property do this?

This is my code.

<RibbonTab Header="Tab 1"><Button Content="Button" Height="Auto" Width="Auto"/></RibbonTab>

Thanks,

IamHuM