Link with Workflow-Variable

I'm trying to create dynamically a link in a "Task description" of an "Assign Flexi task" action configuration in Nintex Workflow 2013.

I've selected the tab "INSERT" and then "Link".  If the value in the "Adress" textbox is static, everything works fine. But if I insert a  Workflow variable like {WorkflowVariable:MyHyperlink} it renders like this:

My dynamically created link: http://server:8081/list.aspx?page=42&bookmark=25%3BJAAAAACLAQAAAAJ7BDEAMAAwADM=&mode=view" nw="true">Link-Text

The whole text ("http://server:8081/list.aspx?page=42&bookmark=25%3BJAAAAACLAQAAAAJ7BDEAMAAwADM=&mode=view" nw="true">Link-Text") is blue and a mouseover changes the mouse to a cursor (instead of a hand!).

How can I create a link dynamically?