diff --git a/util/migrate/allocator.py b/util/migrate/allocator.py
index c0502a843..bf998e1dd 100644
--- a/util/migrate/allocator.py
+++ b/util/migrate/allocator.py
@@ -14,9 +14,9 @@ class NoAvailableKeysError(ValueError):
 
 
 class CompletedKeys(object):
-  def __init__(self, max_index):
+  def __init__(self, min_index, max_index):
     self._max_index = max_index
-    self._min_index = 0
+    self._min_index = min_index
     self._slabs = RBTree()
 
   def _get_previous_or_none(self, index):
@@ -118,7 +118,7 @@ class CompletedKeys(object):
     return random.randint(hole_start, rand_max_bound)
 
 
-def yield_random_entries(batch_query, primary_key_field, batch_size, max_id):
+def yield_random_entries(batch_query, primary_key_field, batch_size, max_id, min_id=0):
   """ This method will yield items from random blocks in the database. We will track metadata
       about which keys are available for work, and we will complete the backfill when there is no
       more work to be done. The method yields tupes of (candidate, Event), and if the work was
@@ -126,8 +126,9 @@ def yield_random_entries(batch_query, primary_key_field, batch_size, max_id):
       an "id" field which can be inspected.
   """
 
+  min_id = max(min_id, 0)
   max_id = max(max_id, 1)
-  allocator = CompletedKeys(max_id + 1)
+  allocator = CompletedKeys(min_id, max_id + 1)
 
   try:
     while True: