diff --git a/platform_storage_api/storage.py b/platform_storage_api/storage.py
index 06032d55..883ba3c0 100644
--- a/platform_storage_api/storage.py
+++ b/platform_storage_api/storage.py
@@ -189,7 +189,7 @@ async def rename(
 
     @trace
     async def disk_usage(
-        self, path: Optional[Union[PurePath, str]] = None
+        self, path: Union[PurePath, str, None] = None
     ) -> DiskUsageInfo:
         real_path = await self._path_resolver.resolve_path(PurePath(path or "/"))
         return await self._fs.disk_usage(real_path)