Instance of an Activity Parameter?

[Marcel]

Hi.
I have a problem with my Enterprise Architect (Version 7.0818).
I have an activity diagram with some activitys on it. These activitites do have activity parameters.
When I create an invocation of an activity and want to add the activity parameters (also as an instance, by drag&drop the parameters from the project browser onto the diagram), I get an error message:

"When dropping embedded elements on to a diagram, you must drop them on their correct owner"

But I did drop them onto their owner! What is my mistake?
I want to keep on using the activity parameters, because when I realise them as action pins on the invocation, I have redundant information (bad for changings etc).

Thank you!
Greetz
Marcel