diff --git a/Control/AthenaPython/python/Bindings.py b/Control/AthenaPython/python/Bindings.py
index 140083199f69bffabc77193068a63861fa9345fe..392190157ead0d4838a4e5ff0fb147756c3b14d1 100644
--- a/Control/AthenaPython/python/Bindings.py
+++ b/Control/AthenaPython/python/Bindings.py
@@ -104,7 +104,8 @@ class _PyAthenaBindingsCatalog(object):
             _msg = _PyAthenaBindingsCatalog.msg
             _msg.error("Problem registering callback for [%s]", klass)
             _msg.error("Exception: %s", err)
-        _PyAthenaBindingsCatalog.instances[klass] = lambda : None
+            cb = lambda : None  # noqa: E731
+        _PyAthenaBindingsCatalog.instances[klass] = cb
         return
 
     @staticmethod