diff --git a/DDG4/python/DDG4.py b/DDG4/python/DDG4.py
index b009bd0371e7ba6af2b86c9fded52a85c5ebd15d..4a6a45122eb943d96472d1985761a68a376fb172 100644
--- a/DDG4/python/DDG4.py
+++ b/DDG4/python/DDG4.py
@@ -111,7 +111,7 @@ def importConstants(description,namespace=None,debug=False):
           logger.error('+++ FAILED to import: "'+k+'" = "'+str(v)+'"')
       logger.info('+++ %s',100*'=')
 
-    for k,v in todo.items():
+    for k,v in list(todo.items()):
       if not hasattr(ns,k):
         val = evaluator.evaluate(v)
         status = evaluator.status()