diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index e3b478d41..49acba15e 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -138,8 +138,11 @@ So you wanna make a pull request? Please observe the following guidelines.
 - Never use plain strings right in the source code - pull them from `messages.json`!
   You **only** need to modify the default locale
   [`_locales/en/messages.json`](_locales/en/messages.json).
-    Other locales are generated automatically based on that file and then periodically
-    uploaded to Crowdin for translation.
+  Other locales are generated automatically based on that file and then periodically
+  uploaded to Crowdin for translation. If you add or change strings in messages.json
+  you will need to run [`tools/updateI18nKeysType.py`](tools/updateI18nKeysType.py)
+  this script generates updated TypeScript type definitions to ensure you aren't
+  using a localisation key which doesn't exist.
 - Please do not submit pull requests for pure translation fixes. Anyone can update
   the translations at [Crowdin](https://crowdin.com/project/session-desktop).
 - [Rebase](https://nathanleclaire.com/blog/2014/09/14/dont-be-scared-of-git-rebase/) your