diff --git a/CHANGES b/CHANGES
index be7ede79..0c7a8e1e 100644
--- a/CHANGES
+++ b/CHANGES
@@ -13,6 +13,7 @@ Release date to be decided.
   :ref:`upgrading-to-010` for more information.
 - Added ``template_test`` methods in addition to the already existing
   ``template_filter`` method family.
+- Set the content-length header for x-sendfile.
 
 Version 0.9
 -----------
diff --git a/flask/helpers.py b/flask/helpers.py
index b2d34a71..07c8add2 100644
--- a/flask/helpers.py
+++ b/flask/helpers.py
@@ -541,6 +541,7 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
         if file is not None:
             file.close()
         headers['X-Sendfile'] = filename
+        headers['Content-Length'] = os.path.getsize(filename)
         data = None
     else:
         if file is None: