Gst-transitional provision

Dear professional, Please clarify my doubts on the following points- Under the transitional provision it is mentioned that, unutilized credit shown in the return for the period immediately before the appointed date will be carried forward under GST if the said credit is eligible to be carried forward both under GST and existing Act as per section 140 of the GST Act. My issue is suppose I have paid duty under existing Act and they are eligible credit under existing act but they not eligible credit under gst so this will lead to cash loss in respect of duty/tax paid under existig Act.. I hope I have made myself clear.. Please help