"'Tooltip' cannot have a logical or visual parent." when editing style in Blend 4 by JulianDominguez

I am trying to edit the style/template for a WPF tooltip (targeting .NET 3.5), and get an error in Blend saying: "'Tooltip' cannot have a logical or visual parent."
I'm using the following steps to create the style and edit the style: http://www.85turns.com/2009/07/10/editing-a-tooltip-style-in-blend-3/

I cannot find a workaround for this that would allow me to edit the template. Of course I can change the TargetType to ContentControl or something of the sort as a temporary measure, but I won't be able to style and use the specific Tooltip properties.

I'm using Blend 4.0.20525.0 (bundled with SketchFlow and the whole Studio suite)

EDIT: I verified that this is happening in a WPF 4.0 project also.