diff --git a/mlair/data_handler/data_handler_with_filter.py b/mlair/data_handler/data_handler_with_filter.py
index b3274b6981c675794a99f1fdd9330990ceb251be..e7101468117492c9ac0a351ee7d1618563719013 100644
--- a/mlair/data_handler/data_handler_with_filter.py
+++ b/mlair/data_handler/data_handler_with_filter.py
@@ -108,7 +108,7 @@ class DataHandlerFirFilterSingleStation(DataHandlerFilterSingleStation):
 
     _requirements = remove_items(DataHandlerFilterSingleStation.requirements(), "station")
     _hash = DataHandlerFilterSingleStation._hash + ["filter_cutoff_period", "filter_order", "filter_window_type",
-                                                    "filter_add_unfiltered"]
+                                                    "_add_unfiltered"]
 
     DEFAULT_WINDOW_TYPE = ("kaiser", 5)
     DEFAULT_ADD_UNFILTERED = False