diff --git a/youtube_dl/downloader/__init__.py b/youtube_dl/downloader/__init__.py
index 3f941596e..31e28df58 100644
--- a/youtube_dl/downloader/__init__.py
+++ b/youtube_dl/downloader/__init__.py
@@ -30,3 +30,8 @@ def get_suitable_downloader(info_dict):
         return F4mFD
     else:
         return HttpFD
+
+__all__ = [
+    'get_suitable_downloader',
+    'FileDownloader',
+]