diff --git a/tasklib/serializing.py b/tasklib/serializing.py
index 8065811..7f46767 100644
--- a/tasklib/serializing.py
+++ b/tasklib/serializing.py
@@ -173,11 +173,11 @@ def deserialize_annotations(self, data):
         return [TaskAnnotation(self, d) for d in data] if data else []
 
     def serialize_tags(self, tags):
-        return ','.join(tags) if tags else ''
+        return list(tags or [])
 
     def deserialize_tags(self, tags):
         if isinstance(tags, str):
-            return set(tags.split(',')) if tags else set()
+            return set(tags.split(','))
         return set(tags or [])
 
     def serialize_parent(self, parent):