diff --git a/.github/workflows/docker.yaml b/.github/workflows/docker.yaml
index ffc05606..8787e550 100644
--- a/.github/workflows/docker.yaml
+++ b/.github/workflows/docker.yaml
@@ -23,8 +23,8 @@ jobs:
         uses: docker/build-push-action@v5
         with:
           push: true
-          build-args:
-            - POETRY_OPTS="--with server"
+          build-args: |
+            POETRY_OPTS="--with server"
           tags: ene-docker.iiasa.ac.at/ixmp4-server:latest
       - if: github.event_name != 'release'
         name: Build and push dev