diff --git a/extra/3RD_PARTY_QUICK_START.md b/extra/3RD_PARTY_QUICK_START.md
index 1d6e7e1152..c325f654a0 100644
--- a/extra/3RD_PARTY_QUICK_START.md
+++ b/extra/3RD_PARTY_QUICK_START.md
@@ -43,6 +43,7 @@ To test (detect and markup tests), just build Highlight.js and test it.  Your te
 node ./tools/build.js -t node
 npm run test
 ```
+(don't forget to run `npm i` before you use npm scripts like test or build for the first time.)
 
 Running the tests this way runs the complete suite of tests for all languages. You can set the `ONLY_EXTRA` environment variable to focus the tests on just the language(s) you are currently working on in the `extra` folder.