DSCallback not fired when json Error

When i have a Incorrect JSN sintax in a webservice response, the callback in datsource is not fired..

public DATA createDataSource(final int Tipo, final String String_Object) {
	 dataSource = new DATA() {
	 protected void transformResponse(DSResponse response, DSRequest request, Object data) {
         GWT.log(response.getStatus()+"-");
....

Result:
1.login: 0
2.test: Error evaluating JSON: SyntaxError: unterminated string lit…

As you can see, the transformResponse is not invoked..

Why?
pd: the bad json sintax is purpose