diff --git a/ostap/fitting/roocollections.py b/ostap/fitting/roocollections.py
index 1cba1fb6..1f12ea2d 100644
--- a/ostap/fitting/roocollections.py
+++ b/ostap/fitting/roocollections.py
@@ -374,7 +374,7 @@ def _stl_contains_ ( lst , item ) :
     _STLList .__str__      = lambda s : str ( tuple ( _rs_list_ ( s ) ) ) if s else '[]'
     _STLList .__repr__     = lambda s : str ( tuple ( _rs_list_ ( s ) ) ) if s else '[]'
     _STLList .__contains__ = _stl_contains_ 
-else ( 6 , 24 ) <= root_info : 
+elif ( 6 , 24 ) <= root_info : 
     _STLList = ROOT.RooSTLRefCountList(ROOT.RooAbsArg)
     _STLList .__str__      = lambda s : str ( tuple ( _rs_list_ ( s ) ) ) if s else '[]'
     _STLList .__repr__     = lambda s : str ( tuple ( _rs_list_ ( s ) ) ) if s else '[]'