diff --git a/tools/zuul/playbooks/docker-image-build.yaml b/tools/zuul/playbooks/docker-image-build.yaml
index d54ec7ff..2a844512 100644
--- a/tools/zuul/playbooks/docker-image-build.yaml
+++ b/tools/zuul/playbooks/docker-image-build.yaml
@@ -60,10 +60,10 @@
     - name: Determine tags
       shell: echo '{{ tags | to_json }}' | python {{ zuul.project.src_dir }}/tools/image_tags.py
       environment:
-        BRANCH: "{{ zuul.branch }}"
-        CHANGE: "{{ zuul.change }}"
+        BRANCH: "{{ zuul.branch | default('') }}"
+        CHANGE: "{{ zuul.change | default('')  }}"
         COMMIT: "{{ zuul.newrev | default('') }}"
-        PATCHSET: "{{ zuul.patchset }}"
+        PATCHSET: "{{ zuul.patchset | default('')  }}"
       register: image_tags
 
     - name: Debug computed tags