diff --git a/tools/uncompressedsize.py b/tools/uncompressedsize.py
index 732db7167..32ba0957c 100644
--- a/tools/uncompressedsize.py
+++ b/tools/uncompressedsize.py
@@ -1,12 +1,15 @@
+import json
+import logging
+
 from data import model
 from data.database import ImageStorage
 from app import app, storage as store
 from data.database import db
 
-import logging
 
 logger = logging.getLogger(__name__)
 
+
 def backfill_sizes():
   query = (ImageStorage
            .select()
@@ -31,7 +34,8 @@ def backfill_sizes():
         uuid = image_storage.uuid
         with_locations = model.get_storage_by_uuid(uuid)
 
-        json_data = store.get_content(with_locations.locations, store.image_json_path(uuid))
+        json_string = store.get_content(with_locations.locations, store.image_json_path(uuid))
+        json_data = json.loads(json_string)
         size = json_data.get('Size', json_data.get('size', -1))
 
         if size == -1: