diff --git a/api/extensions/storage/base_storage.py b/api/extensions/storage/base_storage.py
index b987c7d253..a73d429ccd 100644
--- a/api/extensions/storage/base_storage.py
+++ b/api/extensions/storage/base_storage.py
@@ -20,11 +20,11 @@ class BaseStorage(ABC):
         raise NotImplementedError
 
     @abstractmethod
-    def download(self, filename, target_filepath):
+    def download(self, filename: str, target_filepath: str) -> None:
         raise NotImplementedError
 
     @abstractmethod
-    def exists(self, filename):
+    def exists(self, filename: str) -> bool:
         raise NotImplementedError
 
     @abstractmethod