diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 6939ebb1b..b5e3d9558 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -229,7 +229,7 @@ jobs:
       - name: Generate Docker image tag
         id: tag
         run: |
-          if [[ $(grep "pull" <<< "${GITHUB_REF}") ]]; then
+          if [[ "${GITHUB_EVENT_NAME}" == "pull_request_target" ]]; then
             IMAGE_TAG=$(echo "${GITHUB_HEAD_REF}" | sed "s#/#-#g")
           else
             IMAGE_TAG=$(echo "${GITHUB_REF:11}" | sed "s#/#-#g")