diff --git a/ckan/exceptions.py b/ckan/exceptions.py
index 5bcc92491e6..bd0d009e892 100644
--- a/ckan/exceptions.py
+++ b/ckan/exceptions.py
@@ -1,12 +1,16 @@
+# -*- coding: utf-8 -*-
 class CkanException(Exception):
     pass
 
+
 class EmptyRevisionException(CkanException):
     pass
 
+
 class CkanUrlException(Exception):
     pass
 
+
 class CkanVersionException(Exception):
     '''Exception raised by
     :py:func:`~ckan.plugins.toolkit.requires_ckan_version` if the required CKAN
@@ -15,5 +19,14 @@ class CkanVersionException(Exception):
     '''
     pass
 
+
 class CkanConfigurationException(Exception):
     pass
+
+
+class HelperError(Exception):
+    """Raised if an attempt to access an undefined helper is made.
+
+    Normally, this would be a subclass of AttributeError, but Jinja2 will
+    catch and ignore them. We want this to be an explicit failure re #2908.
+    """
diff --git a/ckan/lib/helpers.py b/ckan/lib/helpers.py
index 1394a53d1bf..514f46dcab5 100644
--- a/ckan/lib/helpers.py
+++ b/ckan/lib/helpers.py
@@ -50,14 +50,6 @@
 log = logging.getLogger(__name__)
 
 
-class HelperError(Exception):
-    """Raised if an attempt to access an undefined helper is made.
-
-    Normally, this would be a subclass of AttributeError, but Jinja2 will
-    catch and ignore them. We want this to be an explicit failure re #2908.
-    """
-
-
 class AttributeDict(dict):
     def __init__(self, *args, **kwargs):
         super(AttributeDict, self).__init__(*args, **kwargs)
@@ -67,7 +59,7 @@ def __getitem__(self, key):
         try:
             value = super(AttributeDict, self).__getitem__(self, key)
         except AttributeError:
-            raise HelperError(
+            raise ckan.exceptions.HelperError(
                 'Helper \'{key}\' has not been defined.'.format(
                     key=key
                 )