CDC Control Task: Failed to update database '' because it is readonly

I am attempting to use the new CDC components in SSIS 2012.  Our DBAs have setup CDC in the primary OLTP system, and a database mirror to a secondary readonly database.  I have configured the CDC control task to Mark Initial Load Start, a dataflow task that uses a CDC Source component, then another CDC control task to Mark Initial Load End.  When I run the package, it get an error on the first CDC control task:  CDC Control Task: 'Failed to update database '' because it is readonly'.  I set the ApplicationIntent property on my Connection manager to "ReadOnly".  My question/confusion is what is the component trying to update?  My understanding of the way the components work is that they track the LSNs, which seems like a readonly process.

Thanks in advance!

jchiking