diff --git a/notebook/terminal/handlers.py b/notebook/terminal/handlers.py
index d8f83056b..9cd41f56b 100644
--- a/notebook/terminal/handlers.py
+++ b/notebook/terminal/handlers.py
@@ -9,6 +9,12 @@ from tornado import web
 import terminado
 from ..base.handlers import IPythonHandler
 
+try:
+    from urllib.parse import urlparse # Py 3
+except ImportError:
+    from urlparse import urlparse # Py 2
+
+
 class TerminalHandler(IPythonHandler):
     """Render the terminal interface."""
     @web.authenticated
@@ -17,8 +23,53 @@ class TerminalHandler(IPythonHandler):
                    ws_path="terminals/websocket/%s" % term_name))
 
 class TermSocket(terminado.TermSocket, IPythonHandler):
+
     def set_default_headers(self):
         pass
+
+    def check_origin(self, origin):
+        """Check Origin for cross-site websockets, required opt-in for Tornado>4
+
+        Copied from APIHandler in handlers (which was in turn copied from WebSocket with changes)
+
+        """
+        if self.allow_origin == '*':
+            return True
+
+        host = self.request.headers.get("Host")
+        origin = self.request.headers.get("Origin")
+
+        # If no header is provided, assume it comes from a script/curl.
+        # We are only concerned with cross-site browser stuff here.
+        if origin is None or host is None:
+            return True
+
+        origin = origin.lower()
+        origin_host = urlparse(origin).netloc
+
+        # OK if origin matches host
+        if origin_host == host:
+            return True
+
+        # Check CORS headers
+        if self.allow_origin:
+            allow = self.allow_origin == origin
+        elif self.allow_origin_pat:
+            allow = bool(self.allow_origin_pat.match(origin))
+        else:
+            # No CORS headers deny the request
+            allow = False
+        if not allow:
+            self.log.warn("Blocking Cross Origin WebSocket request.  Origin: %s, Host: %s",
+                origin, host,
+            )
+        return allow
+
+    def origin_check(self):
+        """Override Terminado's origin_check with our own check_origin, confusingly"""
+        origin = self.request.headers.get("Origin")
+        return self.check_origin(origin)
+
     
     def get(self, *args, **kwargs):
         if not self.get_current_user():