diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 7f7f181..c168f32 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -18,7 +18,7 @@ jobs:
 
     - name: Build
       env:
-        BRANCH_NAME: ${GITHUB_REF#refs/heads/}
+        BRANCH_NAME: ${{ GITHUB_REF#refs/heads/ }}
       run: |
         cd app
         echo "testing GITHUB_REF itself: $GITHUB_REF"