Adding throws Exception to AggregationStrategy.aggregate - Camel 2.9.0

I'm attempting to implement an AggregationStrategy and running into issues
when I try to add a throws Exception to the aggregate interface. The
aggregate is aggregating and enhancing the elements being aggregated at the
same time.

Database look ups are being loaded for evaluation of aggregation and then
additional elements on the exchanges are populated. These operations may
throws exceptions (rarely) but I'd still like my exception router to handle
them.

Suggestions?

Camel 2.9.0 is the camel version.