diff --git a/plsc_ordered.py b/plsc_ordered.py
index ff23629..dc52b52 100755
--- a/plsc_ordered.py
+++ b/plsc_ordered.py
@@ -100,7 +100,7 @@ def res(days, interval):
 
     # clean up the lists, such that we return empty lists if no attribute is present, rather than [None]
     for key, val in record.items():
-        record[key] = list(filter(None, record[key]))
+        record[key] = list(filter(lambda n: n is not None, val))
 
     rdn = f"uid={username}"