diff --git a/.github/workflows/deploy-dataflow-flex-template.yml b/.github/workflows/deploy-dataflow-flex-template.yml
index e459d19..e258bc1 100644
--- a/.github/workflows/deploy-dataflow-flex-template.yml
+++ b/.github/workflows/deploy-dataflow-flex-template.yml
@@ -29,6 +29,10 @@ jobs:
         id: build_flex_template
         run: echo "BUILD_TAG=$(./build_flex_template.sh | tail -1)" >> $GITHUB_OUTPUT
         shell: bash
+      - name: Check BUILD_TAG
+        # Fail the run if the BUILD_TAG is empty
+        if: ${{ steps.build_flex_template.outputs.BUILD_TAG == '' }}
+        run: exit 1
       - name: Update Cloud Workflow build tag
         # yamllint disable rule:line-length
         run: sed -ri 's/^(\s*-\sflexTemplateBuildTag:)(\s".*"$)/\1 "${{ steps.build_flex_template.outputs.BUILD_TAG }}"/' data-pipeline.workflows.yaml