diff --git a/worlds/AutoWorld.py b/worlds/AutoWorld.py
index 02b94c5f..8d9a1b08 100644
--- a/worlds/AutoWorld.py
+++ b/worlds/AutoWorld.py
@@ -27,7 +27,8 @@ class AutoWorldRegister(type):
 
         # build rest
         dct["item_names"] = frozenset(dct["item_name_to_id"])
-        dct["item_name_groups"] = dct.get("item_name_groups", {})
+        dct["item_name_groups"] = {group_name: frozenset(group_set) for group_name, group_set
+                                   in dct.get("item_name_groups", {}).items()}
         dct["item_name_groups"]["Everything"] = dct["item_names"]
         dct["location_names"] = frozenset(dct["location_name_to_id"])
         dct["all_item_and_group_names"] = frozenset(dct["item_names"] | set(dct.get("item_name_groups", {})))