diff --git a/openfisca_core/variables/variable.py b/openfisca_core/variables/variable.py
index 21844dd13..f0a88ea8d 100644
--- a/openfisca_core/variables/variable.py
+++ b/openfisca_core/variables/variable.py
@@ -365,7 +365,10 @@ def is_input_variable(self):
 
     @classmethod
     def get_introspection_data(cls):
-        return cls.introspection_data
+        try:
+            return cls.introspection_data
+        except AttributeError:
+            return '', None, 0
 
     def get_formula(
         self,