diff --git a/ItemList.py b/ItemList.py
index 94ca5761..6c0d671f 100644
--- a/ItemList.py
+++ b/ItemList.py
@@ -356,9 +356,9 @@ def generate_itempool(world, player):
     # logic has some branches where having 4 hearts is one possible requirement (of several alternatives)
     # rather than making all hearts/heart pieces progression items (which slows down generation considerably)
     # We mark one random heart container as an advancement item (or 4 heart pieces in expert mode)
-    if world.difficulty[player] in ['normal', 'hard'] and not (world.custom and world.customitemarray[player]["heartcontainer"] == 0):
+    if world.difficulty[player] in ['normal', 'hard'] and not (world.custom and player in world.customitemarray and world.customitemarray[player]["heartcontainer"] == 0):
         next(item for item in items if item.name == 'Boss Heart Container').advancement = True
-    elif world.difficulty[player] in ['expert'] and not (world.custom and world.customitemarray[player]["heartpiece"] < 4):
+    elif world.difficulty[player] in ['expert'] and not (world.custom and player in world.customitemarray and world.customitemarray[player]["heartpiece"] < 4):
         adv_heart_pieces = (item for item in items if item.name == 'Piece of Heart')
         for i in range(4):
             next(adv_heart_pieces).advancement = True