ContextMenu for Tabs

How can I override the ContextMenu on the tab headers? I want to have my own menuItems when a user right-clicks on the tab header. I've added the context menu to each of the elements, and it doesn't seem to make it available where I'd expect. 

            <docking:DockSite Name="m_scriptEditorDockSite" CanDocumentWindowsFloat="False"
                              CanDocumentWindowsDragToLinkedDockSites="False" KeyDown="OnKeyDown">
                <docking:Workspace>
                    <docking:TabbedMdiHost AllowDrop="False">
                        <docking:TabbedMdiContainer>
                        </docking:TabbedMdiContainer>
                    </docking:TabbedMdiHost>
                </docking:Workspace>
            </docking:DockSite>