diff --git a/backend/union/upstream/upstream.go b/backend/union/upstream/upstream.go
index 99973f9e2..93bce52e9 100644
--- a/backend/union/upstream/upstream.go
+++ b/backend/union/upstream/upstream.go
@@ -90,7 +90,7 @@ func New(ctx context.Context, remote, root string, cacheTime time.Duration) (*Fs
 		return nil, err
 	}
 	f.RootFs = rFs
-	rootString := path.Join(fsPath, filepath.ToSlash(root))
+	rootString := path.Join(remote, filepath.ToSlash(root))
 	myFs, err := cache.Get(ctx, rootString)
 	if err != nil && err != fs.ErrorIsFile {
 		return nil, err