diff --git a/v2/event_attr.py b/v2/event_attr.py
index aa2c4c6..72a4477 100644
--- a/v2/event_attr.py
+++ b/v2/event_attr.py
@@ -11,7 +11,7 @@ class EventAttr:
         attr = self.event_attr.get(key)
         if not attr:
             self.event_attr[key] = self.rdb.smembers(key) or set()
-        return self.event_attr[key]
+        return set(self.event_attr[key])
 
     def set_event_attr(self, key, *data):
         self.rdb.sadd(key, *data)