diff --git a/app/ui.py b/app/ui.py
index 695f5e2..96f807a 100644
--- a/app/ui.py
+++ b/app/ui.py
@@ -796,7 +796,7 @@ def object_presign(bucket_name: str, object_key: str):
     
     api_base = current_app.config.get("API_BASE_URL") or "http://127.0.0.1:5000"
     api_base = api_base.rstrip("/")
-    encoded_key = quote(object_key, safe="")
+    encoded_key = quote(object_key, safe="/")
     url = f"{api_base}/presign/{bucket_name}/{encoded_key}"
     
     # Use API base URL for forwarded headers so presigned URLs point to API, not UI