Exclude folder / find in path

I'm trying to exclude a build folder from search as per the post here:

https://stackoverflow.com/questions/29014063/ignore-a-folder-in-search-results

I'm following Darek Kays method - but it's not working.

I'm using IntelliJ 2018.

As you can see from the following screenshot files from the build folder continue to be shown despite the fact build is excluded - and marked as so red.

http://i.imgur.com/lmYLt64.png

Am I missing something?