Can't do a POST request with xmlData in extjs5

Hello,

As a result of upgrading from extjs 4.2.1 to extjs 5, I can no longer do a POST request using the xmlData property. I got this working in extjs4 by overriding the buildRequest method in Ext.data.proxy.Ajax. In the override, I'd manually assign the xmlData property with my XML info. This no longer works in extJS5. Does anyone know what has changed?

Can't do a POST request with xmlData in extjs5