diff --git a/flask_pymongo/__init__.py b/flask_pymongo/__init__.py
index 896c485..3001684 100644
--- a/flask_pymongo/__init__.py
+++ b/flask_pymongo/__init__.py
@@ -183,6 +183,7 @@ def get_upload(filename):
 
     def save_file(self, filename, fileobj, base="fs", content_type=None, **kwargs):
         """Save a file-like object to GridFS using the given filename.
+           Return the "_id" of the created file.
 
         .. code-block:: python