diff --git a/orchestra/contrib/bills/admin.py b/orchestra/contrib/bills/admin.py
index c7c4fc43..7ef0c78e 100644
--- a/orchestra/contrib/bills/admin.py
+++ b/orchestra/contrib/bills/admin.py
@@ -16,7 +16,7 @@ from orchestra.admin import ExtendedModelAdmin
 from orchestra.admin.utils import admin_date, insertattr, admin_link, change_url
 from orchestra.contrib.accounts.actions import list_accounts
 from orchestra.contrib.accounts.admin import AccountAdminMixin, AccountAdmin
-from orchestra.forms.widgets import paddingCheckboxSelectMultiple
+from orchestra.forms.widgets import PaddingCheckboxSelectMultiple
 
 from . import settings, actions
 from .filters import (BillTypeListFilter, HasBillContactListFilter, TotalListFilter,
@@ -483,7 +483,7 @@ class BillContactInline(admin.StackedInline):
         if db_field.name == 'address':
             kwargs['widget'] = forms.Textarea(attrs={'cols': 70, 'rows': 2})
         if db_field.name == 'email_usage':
-            kwargs['widget'] = paddingCheckboxSelectMultiple(45)
+            kwargs['widget'] = PaddingCheckboxSelectMultiple(45)
         return super().formfield_for_dbfield(db_field, **kwargs)
 
 
diff --git a/orchestra/contrib/contacts/admin.py b/orchestra/contrib/contacts/admin.py
index f761fc28..82adc381 100644
--- a/orchestra/contrib/contacts/admin.py
+++ b/orchestra/contrib/contacts/admin.py
@@ -7,7 +7,7 @@ from orchestra.admin.actions import SendEmail
 from orchestra.admin.utils import insertattr, change_url
 from orchestra.contrib.accounts.actions import list_accounts
 from orchestra.contrib.accounts.admin import AccountAdmin, AccountAdminMixin
-from orchestra.forms.widgets import paddingCheckboxSelectMultiple
+from orchestra.forms.widgets import PaddingCheckboxSelectMultiple
 
 from .filters import EmailUsageListFilter
 from .models import Contact
@@ -61,18 +61,18 @@ class ContactAdmin(AccountAdminMixin, ExtendedModelAdmin):
         }),
     )
     actions = (SendEmail(), list_accounts)
-    
+
     def dispaly_name(self, contact):
         return str(contact)
     dispaly_name.short_description = _("Name")
     dispaly_name.admin_order_field = 'short_name'
-    
+
     def formfield_for_dbfield(self, db_field, **kwargs):
         """ Make value input widget bigger """
         if db_field.name == 'address':
             kwargs['widget'] = forms.Textarea(attrs={'cols': 70, 'rows': 2})
         if db_field.name == 'email_usage':
-            kwargs['widget'] = paddingCheckboxSelectMultiple(130)
+            kwargs['widget'] = PaddingCheckboxSelectMultiple(130)
         return super(ContactAdmin, self).formfield_for_dbfield(db_field, **kwargs)
 
 
@@ -86,14 +86,14 @@ class ContactInline(admin.StackedInline):
     fields = (
         ('short_name', 'full_name'), 'email', 'email_usage', ('phone', 'phone2'),
     )
-    
+
     def get_extra(self, request, obj=None, **kwargs):
        return 0 if obj and obj.contacts.exists() else 1
-    
+
     def get_view_on_site_url(self, obj=None):
         if obj:
             return change_url(obj)
-    
+
     def formfield_for_dbfield(self, db_field, **kwargs):
         """ Make value input widget bigger """
         if db_field.name == 'short_name':
@@ -101,7 +101,7 @@ class ContactInline(admin.StackedInline):
         if db_field.name == 'address':
             kwargs['widget'] = forms.Textarea(attrs={'cols': 70, 'rows': 2})
         if db_field.name == 'email_usage':
-            kwargs['widget'] = paddingCheckboxSelectMultiple(45)
+            kwargs['widget'] = PaddingCheckboxSelectMultiple(45)
         return super(ContactInline, self).formfield_for_dbfield(db_field, **kwargs)
 
 
diff --git a/orchestra/contrib/orchestration/forms.py b/orchestra/contrib/orchestration/forms.py
index bd3f96ad..7ea33538 100644
--- a/orchestra/contrib/orchestration/forms.py
+++ b/orchestra/contrib/orchestration/forms.py
@@ -1,6 +1,6 @@
 from django import forms
 
-from orchestra.forms.widgets import SpanWidget, paddingCheckboxSelectMultiple
+from orchestra.forms.widgets import SpanWidget, PaddingCheckboxSelectMultiple
 
 
 class RouteForm(forms.ModelForm):
@@ -16,5 +16,5 @@ class RouteForm(forms.ModelForm):
             else:
                 self.fields['backend'].widget = SpanWidget()
                 actions = backend_class.actions
-                self.fields['async_actions'].widget = paddingCheckboxSelectMultiple(45)
+                self.fields['async_actions'].widget = PaddingCheckboxSelectMultiple(45)
                 self.fields['async_actions'].choices = ((action, action) for action in actions)
diff --git a/orchestra/forms/widgets.py b/orchestra/forms/widgets.py
index 0235db61..74a0fd29 100644
--- a/orchestra/forms/widgets.py
+++ b/orchestra/forms/widgets.py
@@ -37,17 +37,17 @@ class SpanWidget(forms.Widget):
         return False
 
 
-def paddingCheckboxSelectMultiple(padding):
+class PaddingCheckboxSelectMultiple(forms.CheckboxSelectMultiple):
     """ Ugly hack to render this widget nicely on Django admin """
-    widget = forms.CheckboxSelectMultiple()
-    old_render = widget.render
+    def __init__(self, padding, attrs=None, choices=()):
+        super().__init__(attrs=attrs, choices=choices)
+        self.padding = padding
+
     def render(self, *args, **kwargs):
-        value = old_render(self, *args, **kwargs)
+        value = super().render(*args, **kwargs)
         value = re.sub(r'^<ul id=([^>]+)>',
-            r'<ul id=\1 style="padding-left:%ipx">' % padding, value, 1)
+            r'<ul id=\1 style="padding-left:%ipx">' % self.padding, value, 1)
         return mark_safe(value)
-    widget.render = render
-    return widget
 
 
 class DynamicHelpTextSelect(forms.Select):