diff --git a/mayan/apps/ocr/backends/__init__.py b/mayan/apps/ocr/backends/__init__.py
index 42ac15c33b..6c671fa564 100644
--- a/mayan/apps/ocr/backends/__init__.py
+++ b/mayan/apps/ocr/backends/__init__.py
@@ -1,3 +1,3 @@
 class BackendBase(object):
-    def execute(input_filename, language=None):
-        raise NotImplemented
+    def execute(input_filename, language=None):  # NOQA
+        raise NotImplementedError
diff --git a/mayan/apps/statistics/classes.py b/mayan/apps/statistics/classes.py
index 0b9e633213..329f6843fd 100644
--- a/mayan/apps/statistics/classes.py
+++ b/mayan/apps/statistics/classes.py
@@ -51,7 +51,7 @@ class Statistic(object):
         return unicode(self.label)
 
     def get_results(self, *args, **kwargs):
-        return NotImplemented
+        return NotImplementedError
 
     @property
     def id(self):