Ol3 cluster works in minified file but not in debug file

I am trying to replicate cluster example from openlayers 3.

It works with the the minified ol.js but with ol-debug.js the map is blank. On inspecting the layer fill and stroke attributes are null when using ol-debug.js.

what is happening, i need to use ol-debug for testing but it is not giving correct result even when code is correct?