diff --git a/src/scgenerator/variableparameters.py b/src/scgenerator/variableparameters.py
index 4b8b316..c3a3f16 100644
--- a/src/scgenerator/variableparameters.py
+++ b/src/scgenerator/variableparameters.py
@@ -439,6 +439,8 @@ else:
             return np.prod(self.__variables_nums__)
 
         setattr(cls, "filter", create_filter(_vfields))
-        setattr(cls, "__len__", _config_len)
+        setattr(cls, "__vlen__", _config_len)
+        if not hasattr(cls, "__len__"):
+            setattr(cls, "__len__", _config_len)
 
         return cls