diff --git a/.github/workflows/docker.yml b/.github/workflows/docker.yml
index 1c422fe..eb86edf 100644
--- a/.github/workflows/docker.yml
+++ b/.github/workflows/docker.yml
@@ -32,7 +32,7 @@ jobs:
         run: echo ::set-output name=tag::${GITHUB_RUN_NUMBER}
 
       - name: Convert repository owner to lowercase
-        run: echo "::set-env name=REPOSITORY_OWNER::${{ github.repository_owner | lower }}"
+        run: echo "::set-env name=REPOSITORY_OWNER::${{ github.repository_owner.lowercase }}"
 
       - name: Build the Docker image
         run: docker build --file Dockerfile --tag ghcr.io/${{ env.REPOSITORY_OWNER }}/${{ env.IMAGE_NAME }}:${{ steps.generate_tag.outputs.tag }} --tag ghcr.io/${{ env.REPOSITORY_OWNER }}/${{ env.IMAGE_NAME }}:latest --build-arg BUILD_DATE=${BUILD_DATE} .