diff --git a/hipposerve/settings.py b/hipposerve/settings.py
index 923d071..28d3629 100644
--- a/hipposerve/settings.py
+++ b/hipposerve/settings.py
@@ -11,7 +11,7 @@
 
 class Settings(BaseSettings):
     minio_url: str
-    minio_presign_url: str | None
+    minio_presign_url: str | None = None
     minio_access: str
     minio_secret: str