diff --git a/backend/app/models.py b/backend/app/models.py
index 8de3ac1..12cb0f5 100644
--- a/backend/app/models.py
+++ b/backend/app/models.py
@@ -1,4 +1,4 @@
-from datetime import datetime, timezone
+from datetime import datetime
 
 from sqlalchemy import (
     Column,
@@ -158,4 +158,4 @@ class StorageBlob(Base):
     content_type = Column(String(100), nullable=False)
     size = Column(Integer, nullable=False)
     data = Column(LargeBinary, nullable=False)
-    created_at = Column(DateTime, nullable=False, default=lambda: datetime.now(timezone.utc))
+    created_at = Column(DateTime, nullable=False, default=datetime.utcnow)