diff --git a/.github/workflows/CheckMainFile.yml b/.github/workflows/CheckMainFile.yml
index 000d4fd..e6d913c 100644
--- a/.github/workflows/CheckMainFile.yml
+++ b/.github/workflows/CheckMainFile.yml
@@ -7,6 +7,7 @@ jobs:
     - uses: actions/checkout@v2
     - name: Check if CookieMonster.js is built correctly 
       run: |
+        npm install
         terser ./src/Header.js ./src/Cache.js ./src/Config.js ./src/Data.js ./src/Disp.js ./src/Main.js ./src/Sim.js ./src/Footer.js -o CookieMonsterTest.js
         if cmp CookieMonster.js CookieMonsterTest.js; then
             echo '### SUCCESS: CookieMonster is correctly built! ###'