diff --git a/datapreparation/data_preparation.py b/datapreparation/data_preparation.py
index f689b2a58298e5e91d6957d838dbf5177ec22555..74abb7dc23bd07a8d6d3950002875d735b686dc5 100644
--- a/datapreparation/data_preparation.py
+++ b/datapreparation/data_preparation.py
@@ -186,8 +186,8 @@ for dd in range(t_interval.days+1):
     # save results
     datestr = str(startdate+dd)
     datestr = datestr.replace("-","")    
-    fn =  datestr + '_bec3.txt'
-    result.to_csv(path_res + fn, index = False)
+    fns =  datestr + '_bec3.txt'
+    result.to_csv(path_res + fns, index = False)
     
     
 #%% data from sql lite database