diff --git a/util/migrate/backfill_aggregate_sizes.py b/util/migrate/backfill_aggregate_sizes.py
index 8e624753b..db6f195f2 100644
--- a/util/migrate/backfill_aggregate_sizes.py
+++ b/util/migrate/backfill_aggregate_sizes.py
@@ -1,44 +1,50 @@
 import logging
 
-from data.database import ImageStorage, Image, db
+from data.database import ImageStorage, Image, db, db_for_update
 from app import app
 
-LOGGER = logging.getLogger(__name__)
+
+logger = logging.getLogger(__name__)
+
 
 def backfill_aggregate_sizes():
   """ Generates aggregate sizes for any image storage entries without them """
-  LOGGER.setLevel(logging.DEBUG)
-  LOGGER.debug('Aggregate sizes backfill: Began execution')
+  logger.debug('Aggregate sizes backfill: Began execution')
   while True:
-    batch_storage_ids = list(ImageStorage
-                          .select(ImageStorage.id)
-                          .where(ImageStorage.aggregate_size >> None)
-                          .limit(10))
+    batch_image_ids = list(Image
+                           .select(Image.id)
+                           .where(Image.aggregate_size >> None)
+                           .limit(100))
 
-    if len(batch_storage_ids) == 0:
+    if len(batch_image_ids) == 0:
       # There are no storages left to backfill. We're done!
-      LOGGER.debug('Aggregate sizes backfill: Backfill completed')
+      logger.debug('Aggregate sizes backfill: Backfill completed')
       return
 
-    LOGGER.debug('Aggregate sizes backfill: Found %s records to update', len(batch_storage_ids))
-    for image_storage_id in batch_storage_ids:
-      LOGGER.debug('Updating image storage: %s', image_storage_id.id)
+    logger.debug('Aggregate sizes backfill: Found %s records to update', len(batch_image_ids))
+    for image_id in batch_image_ids:
+      logger.debug('Updating image : %s', image_id.id)
 
       with app.config['DB_TRANSACTION_FACTORY'](db):
         try:
-          storage = ImageStorage.select().where(ImageStorage.id == image_storage_id.id).get()
-          image  = Image.select().where(Image.storage == storage).get()
+          image = (Image
+                   .select(Image, ImageStorage)
+                   .join(ImageStorage)
+                   .where(Image.id == image_id)
+                   .get())
+
+          aggregate_size = image.storage.image_size
 
           image_ids = image.ancestors.split('/')[1:-1]
-          aggregate_size = storage.image_size
           for image_id in image_ids:
-            current_image = Image.select().where(Image.id == image_id).join(ImageStorage)
-            aggregate_size += image.storage.image_size
+            to_add = db_for_update(Image
+                                   .select(Image, ImageStorage)
+                                   .join(ImageStorage)
+                                   .where(Image.id == image_id)).get()
+            aggregate_size += to_add.storage.image_size
 
-          storage.aggregate_size = aggregate_size
-          storage.save()
-        except ImageStorage.DoesNotExist:
-          pass
+          image.aggregate_size = aggregate_size
+          image.save()
         except Image.DoesNotExist:
           pass