ToolTips Markup Not Showing Formatted Text

I'm trying to add ToolTips to my controls using xtpToolTipMarkup but am not able to see the formatted text. I built a new project, added a single Form, and added a Report control to that form. I added this code in the Load event of the form:

With Me.ReportControl1
  .ToolTipContext.Style = xtpToolTipMarkup
  .ToolTipText = "<TextBlock>Hi</TextBlock>"
End With

When I run the project I see the actual Text, including the <TextBlock> tags. I've also tried this with a TabControl with the same result.

Is there some other setting I should be using? I save the Enablemarkup property of these controls, set that to True but still no change.