Portal Navigation

I am calling a BSP application from my WDA, I pass URL parameters too. Everything works fine, except for, that I added a parameter to the BSP Application (HAP_DOCUMENT), included it in the portal navigation, but the parameter is not available (empty) in the BSP Application. I check the resulting portal URL and it contained the parameter (DynamicParameter=...)

Any idea why the parameter is not passed to the BSP?

René