diff --git a/Pystan/config/sign_analysis.py b/Pystan/config/sign_analysis.py
index 61bd064cf6d836b3edcbf068f5b739187194d229..1988c81fe417dd1d8593f0f5a66546115699d04e 100644
--- a/Pystan/config/sign_analysis.py
+++ b/Pystan/config/sign_analysis.py
@@ -2,7 +2,7 @@
 """
 implements a sign analysis
 """
-from enum import Enum
+from enum import Enum, auto
 from dataclasses import dataclass
 from cfg import Cfg
 from iteration import Transfer, fixpoint_iteration