diff --git a/util/migrate/allocator.py b/util/migrate/allocator.py
index bf998e1dd..8943a50c6 100644
--- a/util/migrate/allocator.py
+++ b/util/migrate/allocator.py
@@ -14,7 +14,7 @@ class NoAvailableKeysError(ValueError):
 
 
 class CompletedKeys(object):
-  def __init__(self, min_index, max_index):
+  def __init__(self, max_index, min_index=0):
     self._max_index = max_index
     self._min_index = min_index
     self._slabs = RBTree()