diff --git a/unoptimized_lr/simple_parser_buses.py b/unoptimized_lr/simple_parser_buses.py
index ce9787edf794b22d349e45d5f33bc060ac3dad52..626bf5682f451851f8a167316e5e9f861252ec52 100644
--- a/unoptimized_lr/simple_parser_buses.py
+++ b/unoptimized_lr/simple_parser_buses.py
@@ -44,7 +44,7 @@ class ParametrizationConstants():
         dummy_signal = Signal(range(longest_serialized_parse_tree))
         self.W_parsetree_index = len(dummy_signal)
 
-        self.W_serialized_parse_tree = max(W_Nonterminal, W_max_RHS, 1 + W_Terminal, 1+ W_parsetree_index)
+        self.W_serialized_parse_tree = max(self.W_nonterminal, self.W_max_RHS, 1 + self.W_terminal, 1+ self.W_parsetree_index)
 
 
 class LR_automaton_internal_layout(Layout):