diff --git a/release_on_tag.py b/release_on_tag.py
index 7ce1ad8bf..babc9940c 100644
--- a/release_on_tag.py
+++ b/release_on_tag.py
@@ -94,7 +94,7 @@ def _upload_asset(release, asset_to_upload, token):
     if is_asset_already_uploaded(release, basename):
         return
     print 'Release upload url:', release.upload_url
-    upload_uri = uritemplate.expand(release.upload_url)
+    upload_uri = uritemplate.expand(release.upload_url, {'name': platform.system()})
     print upload_uri
     print repr(upload_uri)
     print asset_to_upload