XText issue with LiteralValueUse value

I have defined a TDL model programmatically (i.e., a Resource) and I want to save it as a .tdlan2 file. As in the current version of TDL metamodel, the value of the value feature of LiteralValueUse instances is no longer set between quotation marks, when I save the Resource, all LiteralValueUse instances are saved as DataInstanceUse. For example, consider the following TDL model:

Package TestSuite { Type String; Type A (_name of type String); A a (_name = "2"); }

If I save this model as a .tdlan2 file, the result would be:

Package TestSuite { Type String; Type A (_name of type String); A a (_name = 2); }

Here is my code for saving the file:

ResourceSet resSet = new ResourceSetImpl();
	resSet.getResourceFactoryRegistry().getExtensionToFactoryMap().put(".tdlan2", new tdlResourceFactoryImpl());
	resSet.getPackageRegistry().put(tdlPackage.eNS_URI, tdlPackage.eINSTANCE);
	Resource res = resSet.createResource(URI.createURI("path.tdlan2"));
	try {
    		newTestSuiteRes.save(null);
    	} catch (IOException e) {
		e.printStackTrace();
    	}