Document.handler just returns the class, not an instance

src/atom/document.coffee

@@ -11,7 +11,7 @@ class Document extends Pane
   @handlers: {}
   @handler: (path) ->
     for name, {test, handler} of Document.handlers
-      return new handler path if test path
+      return handler if test path
     null
   @register: (test) ->
     Document.handlers[@name] = {test, handler: this}

src/startup.coffee

@@ -30,8 +30,10 @@ for name, method of atom.app
   atom[name] = atom.app[name]
 
 atom.path = $atomController.path.toString()
-atom.document = Document.handler atom.path
-atom.document ?= new Editor
+if handler = Document.handler atom.path
+  atom.document = new handler atom.path
+else
+  atom.document = new Editor
 
 require 'window'
 window.startup()