diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index af8f166ed..357a47552 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -132,6 +132,7 @@ jobs:
     - name: Install dependencies
       run: |
           stack update
+          stack install happy
           stack test --dependencies-only --fast
     - name: Build and test
       shell: cmd