diff --git a/README.md b/README.md
index 0f331f9..b2a8187 100644
--- a/README.md
+++ b/README.md
@@ -120,3 +120,4 @@ lines and a `tags` key, pointing to an array of tags arrays described above.
   * Run `npm test` to run the specs
   * Run `npm run benchmark` to benchmark fully tokenizing jQuery 2.0.3 and
     the CSS for Twitter Bootstrap 3.1.1
+  * If you make changes to `./src/scope-selector-parser.pegjs` ensure to run `npm run parse` to generate the JS form of PegJS.