--- a/tests/test_viewer.py	Sun Jun 19 00:04:48 2016 +0800
+++ b/tests/test_viewer.py	Sun Jun 19 00:18:30 2016 +0800
@@ -21,7 +21,9 @@
     def test_index(self):
         response = self.fetch('/')
         assert response.code == 200
+        assert 'online linter' in response.body
 
     def test_404(self):
         response = self.fetch('/nobodyhere')
         assert response.code == 404
+        assert 'online linter' in response.body

--- a/viewer.py	Sun Jun 19 00:04:48 2016 +0800
+++ b/viewer.py	Sun Jun 19 00:18:30 2016 +0800
@@ -10,6 +10,7 @@
 from tornado.ioloop import IOLoop
 from tornado.options import define, options
 from tornado.web import Application, HTTPError, RequestHandler, URLSpec
+from tornado.web import ErrorHandler as BaseErrorHandler
 
 from candolint import uimodules
 from candolint.models import database, Project, Change, Check
@@ -126,6 +127,10 @@
         self.render('status.svg', width=width, parts=parts, height=20)
 
 
+class ErrorHandler(BaseHandler, BaseErrorHandler):
+    pass
+
+
 class CandolintViewer(Application):
     def __init__(self):
         handlers = [
@@ -133,6 +138,7 @@
             URLSpec(r'/([.a-z0-9_-]+)/([^/]+)/([^/]+)', ProjectHandler),
             URLSpec(r'/([.a-z0-9_-]+)/([^/]+)/([^/]+)/([\d]+|latest)', CheckHandler),
             URLSpec(r'/([.a-z0-9_-]+)/([^/]+)/([^/]+)/status\.svg', StatusHandler),
+            URLSpec(r'.*', ErrorHandler, {'status_code': 404})
         ]
         settings = dict(
             static_path=rel('static'),