diff --git a/deluge/core/filtermanager.py b/deluge/core/filtermanager.py
index 25ae4be1b..b09f39154 100644
--- a/deluge/core/filtermanager.py
+++ b/deluge/core/filtermanager.py
@@ -153,9 +153,8 @@ class FilterManager(component.Component):
 
         #sanitize input: filter-value must be a list of strings
         for key, value in filter_dict.items():
-            if isinstance(value, str):
-                filter_dict[key]  = [value]
-
+            if not isinstance(value, list):
+                filter_dict[key] = [value]
 
         if "id"in filter_dict: #optimized filter for id:
             torrent_ids = list(filter_dict["id"])