Structured Scenarios - merging alternate paths

[bluebird]

I have been generating activity diagrams from a Structured Scenario. Two alternate paths rejoin the basic path at the same point. The generated diagram doesn't render a merge node prior to activity. Instead all the control flows from the various paths converge on the activity.
Adding a merge node to the diagram generates a validation error when trying to generate the scenario from the diagram. Removing the merge node results in a succesful scenario generation.
So my question is this.
1) Can you use merge nodes in structured Scenarios and if so what am I doing wrong? OR
2) If they aren't used is this ok from a UML compliance standpoint - namely it is permissable to relax the UML spec "A merge node is a control node that brings together multiple alternate flows. It is not used to synchronize concurrent flows but to accept one among several alternate flows."?