Using RibbonTab for the Ribbon control in Visual Studio 2012

Using RibbonTab for the Ribbon control in Visual Studio 2012

I have problems using the ribbon control for visual studio 2012. I simply
need to create tabs, but for whatever reason they are not displayed
properly. Here is my code:
<Window x:Class="Arelion.InternalProjects.RouteVisualization.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Route Visualization" Height="350" Width="525">
<Grid>
<Ribbon Name="ribbon">
<RibbonTab Name="ribbonTab1" IsSelected="True">
Tab1
</RibbonTab>
</Ribbon>
</Grid>
</Window>
Thanks