diff --git a/mayan/apps/common/widgets.py b/mayan/apps/common/widgets.py
index 30ac5cb223..1af27ad451 100644
--- a/mayan/apps/common/widgets.py
+++ b/mayan/apps/common/widgets.py
@@ -79,7 +79,7 @@ class NamedMultiWidget(forms.widgets.Widget):
 
     def id_for_label(self, id_):
         if id_:
-            id_ += '_{}'.format(self.widgets.keys()[0])
+            id_ += '_{}'.format(list(self.widgets.keys())[0])
         return id_
 
     def value_from_datadict(self, data, files, name):