diff --git a/src/config-schema.coffee b/src/config-schema.coffee
index 334437618..27f436e09 100644
--- a/src/config-schema.coffee
+++ b/src/config-schema.coffee
@@ -29,6 +29,7 @@ module.exports =
       customFileTypes:
         type: 'object'
         default: {}
+        description: 'Associates scope names (e.g. "source.js") with arrays of file extensions and file names (e.g. ["Somefile", ".js2"])'
         additionalProperties:
           type: 'array'
           items: