diff --git a/rfcs/0001-plugin-index.md b/rfcs/0001-plugin-index.md
index c4ae728..f92c7ef 100644
--- a/rfcs/0001-plugin-index.md
+++ b/rfcs/0001-plugin-index.md
@@ -50,6 +50,7 @@ Each Plugin has its own Manifest, which contains a map with the following conten
 - `homepage`: A valid URL pointing at a page containing more information about the Plugin.
 - `license`: A license identifier in accordance with the [SPDX license list](https://spdx.org/licenses/), or the string `ALL-RIGHTS-RESERVED`.
 - `version`: The Plugin's version, as currently indexed.
+- `file_size`: The size of the file pointed to by `url` in bytes.
 - `shortDescription`:  A short text describing the Plugin. **Should** be less than 150 and **must** be less than 200 characters.
 - `description`:  A text of arbitrary length describing the Plugin, similar to the Plugin's `about.txt`.
 - `url`: A valid URL pointing directly (redirects are allowed) at a Zip-archive containing release `version` of the Plugin.