Facing issue with ListGridRecord formatter

Hi,

We have client only data source enabled. We have extended ListGridRecord to our specialized class and adding this specialized class records to datasource.
Inside cellformatter, we are getting exception when we are trying to cast to our specialized class.

E.G:
Our specialized class name is: FileDescriptorGridRecord which extends ListGridRecord.
Inside Cellformatter:
setCellFormatter(new CellFormatter() {
@Override
public String format(Object value, ListGridRecord record, int rowNum, int colNum) {
record.getAttributes();
FileDescriptorGridRecord fileRecord=(FileDescriptorGridRecord) record;

At this point we are getting excpetion saying:
20:01:13.450 [ERROR] [cm] Uncaught exception escaped

java.lang.ClassCastException: com.smartgwt.client.widgets.grid.ListGridRecord cannot be cast to com.altair.cm.rfb.client.data.FileDescriptorGridRecord at com.altair.cm.rfb.client.FileDescriptorGrid$2.format(FileDescriptorGrid.java:255)

This is happening only after upgrading from 2.3 to 4.1.

Could you please let me know where I am going wrong?

Thanks
Viswanath