diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index c05e348e9..435cfccf6 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -36,6 +36,7 @@ If you want to start contributing to the project's code, please follow these gui
 - Before adding a new feature, ask about it in the [Github Issue Tracker](https://github.com/laurent22/joplin/issues?utf8=%E2%9C%93&q=is%3Aissue) or the [Joplin Forum](https://discourse.joplinapp.org/), or check if existing discussions exist to make sure the new functionality is desired.
 - **Changes that will consist in more than 50 lines of code should be discussed the [Joplin Forum](https://discourse.joplinapp.org/)**, so that you don't spend too much time implementing something that might not be accepted.
 - All the applications share the same backend (database, synchronisation, settings, models, business logic, etc.) so if you change something in the backend in one app, makes sure it still work in the other apps. Usually it does, but keep this in mind.
+- Pull requests that make many changes using an automated tool, like for spell fixing, styling, etc. will not be accepted. An exception would be if the changes have been discussed in the forum and someone has agreed to review **and test** the pull request.
 
 Building the apps is relatively easy - please [see the build instructions](https://github.com/laurent22/joplin/blob/master/BUILD.md) for more details.