Why is 'BusyIndicator' not found?

I am using Silverlight 5 toolkit and I am references that version of Silverlight.Windows.Controls.Toolkit in my silverlight demo.

But I get this error and I do not know what to do

Error 16 The tag 'BusyIndicator' does not exist in XML namespace 'clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Toolkit'. C:\Users\Bobbi\Documents\Visual Studio 2012\Projects\...

How do I get the code to compile?