When asyncListener were not added in Builder and added later on Map LISTENER_SERVICE were never initialized and hence async listeners didn't work when added on map later.
Coverage increased (+2.6%) to 71.375% when pulling 380e5cea3c29588583a9753d2e122035f09f8817 on r0b0ji:issue#54 into 700bddb3f9d5c05fe7156d163eb1d02c0970e4ed on jhalterman:master.
When asyncListener were not added in Builder and added later on Map LISTENER_SERVICE were never initialized and hence async listeners didn't work when added on map later.