diff --git a/km3buu/output.py b/km3buu/output.py
index c5cdd3c3a0da21f7e591d61cca59e763eeb2300a..06140a036c9e8c7d477ce777cff10eeb9b4fb07a 100644
--- a/km3buu/output.py
+++ b/km3buu/output.py
@@ -205,7 +205,7 @@ W2LIST_LOOKUP = {
     "GIBUU_WEIGHT": 19
 }
 
-W2LIST_LENGTH = len(W2LIST_LOOKUP)
+W2LIST_LENGTH = max(W2LIST_LOOKUP.values()) + 1
 
 GIBUU_FIELDNAMES = [
     'weight', 'barcode', 'Px', 'Py', 'Pz', 'E', 'evType', 'lepIn_E',