diff --git a/IPython/html/base/zmqhandlers.py b/IPython/html/base/zmqhandlers.py
index 362c586..1b741ae 100644
--- a/IPython/html/base/zmqhandlers.py
+++ b/IPython/html/base/zmqhandlers.py
@@ -43,29 +43,17 @@ from .handlers import IPythonHandler
 
 class ZMQStreamHandler(websocket.WebSocketHandler):
 
-    def check_origin(self):
-        """Check origin from headers."""
-        origin_header = self.request.headers["Origin"]
-        host = self.request.headers["Host"]
+    def is_cross_origin(self):
+        """Check to see that origin and host match in the headers."""
+        origin_header = self.request.headers.get("Origin")
+        host = self.request.headers.get("Host")
 
         parsed_origin = urlparse(origin_header)
         origin = parsed_origin.netloc
 
         # Check to see that origin matches host directly, including ports
-        if origin != host:
-            self.log.warn("Cross Origin WebSocket Attempt.")
-            raise web.HTTPError(404)
-
-
-    def _execute(self, *args, **kwargs):
-        """Wrap all calls to make sure origin gets checked."""
-
-        # Check to see that origin matches host directly, including ports
-        self.check_origin()
+        return origin != host
 
-        # Pass on the rest of the handling by the WebSocketHandler
-        super(ZMQStreamHandler, self)._execute(*args, **kwargs)
-    
     def clear_cookie(self, *args, **kwargs):
         """meaningless for websockets"""
         pass
@@ -114,6 +102,11 @@ class ZMQStreamHandler(websocket.WebSocketHandler):
 class AuthenticatedZMQStreamHandler(ZMQStreamHandler, IPythonHandler):
 
     def open(self, kernel_id):
+        # Check to see that origin matches host directly, including ports
+        if self.is_cross_origin():
+            self.log.warn("Cross Origin WebSocket Attempt.")
+            raise web.HTTPError(404)
+
         self.kernel_id = cast_unicode(kernel_id, 'ascii')
         self.session = Session(config=self.config)
         self.save_on_message = self.on_message
@@ -142,4 +135,4 @@ class AuthenticatedZMQStreamHandler(ZMQStreamHandler, IPythonHandler):
         if self.get_current_user() is None:
             self.log.warn("Couldn't authenticate WebSocket connection")
             raise web.HTTPError(403)
-        self.on_message = self.save_on_message
\ No newline at end of file
+        self.on_message = self.save_on_message