Error using $ref in allOf

[JJCLane]

With an allOf property set like this, the following error is thrown:

"allOf": [
     {
           "$ref": "OrderCreatedEvent.json"
     }
],

In DefinitionsGenerator.php line 116:
                                                                                            
  error generating definition 'Output\OrderCreatedEvent': unsupported '$ref' in 'allOf' type definition                                                                             
                                                                                            

In IntersectProperty.php line 149:
                                                 
  unsupported '$ref' in 'allOf' type definition