Application/Window icon is not getting displayed in QAT RibbonControl

Question

I am working with a WPF application where I have a Ribbon. I also have a Quick Access Toolbar (QAT). As you can see here the window/application icon is not being displayed, rather that place is empty.

I searched a lot, I even tried RibbonWindow and still the place is empty in QAT. Kindly let me know if I am missing any property that I should set?

My xaml:

    <r:Ribbon.QuickAccessToolBar>
        <r:RibbonQuickAccessToolBar  CanUserCustomize="True" >
           <r:RibbonButton Command="{StaticResource cmdAddNew}" Name="qaAddNew" r:RibbonQuickAccessToolBar.Placement="InCustomizeMenuAndToolBar" />
           <r:RibbonButton Command="{StaticResource cmdSave}"   r:RibbonQuickAccessToolBar.Placement="InCustomizeMenuAndToolBar" />
           <r:RibbonButton Command="{StaticResource cmdClose}" Name="qaClose" r:RibbonQuickAccessToolBar.Placement="InCustomizeMenuAndToolBar" />
           <r:RibbonButton Command="{StaticResource cmdReset}"  r:RibbonQuickAccessToolBar.Placement="InCustomizeMenuAndToolBar" />
        </r:RibbonQuickAccessToolBar>           
    </r:Ribbon.QuickAccessToolBar>