diff --git a/roles/build-diskimage/README.rst b/roles/build-diskimage/README.rst
index 1e9a1b3d7..42d010a06 100644
--- a/roles/build-diskimage/README.rst
+++ b/roles/build-diskimage/README.rst
@@ -27,6 +27,7 @@ Example:
    {{ ensure_dib_command }}. as being set by the ensure-dib role.
 
 .. zuul:rolevar:: build_diskimage_image_name
+   :default: "{{ zuul.image_build_name }}"
 
    Name of the image to build.
 
diff --git a/roles/build-diskimage/defaults/main.yaml b/roles/build-diskimage/defaults/main.yaml
index 635ff1870..3ea96ec3f 100644
--- a/roles/build-diskimage/defaults/main.yaml
+++ b/roles/build-diskimage/defaults/main.yaml
@@ -1,4 +1,7 @@
 build_diskimage_command: "{{ ensure_dib_command }}"
+# If used within a non-image-build context this variable needs to be explicitly
+# defined. The role uses a 'mandatory' filter to ensure it is set
+build_diskimage_image_name: "{{ zuul.image_build_name }}"
 
 build_diskimage_formats:
   - qcow2
diff --git a/zuul.d/dib-jobs.yaml b/zuul.d/dib-jobs.yaml
index 08958ebd3..c7c6e330f 100644
--- a/zuul.d/dib-jobs.yaml
+++ b/zuul.d/dib-jobs.yaml
@@ -11,6 +11,7 @@
       or prepare it to be uploaded to log storage.
 
       .. zuul:jobvar:: build_diskimage_image_name
+         :default: "{{ zuul.image_build_name }}"
 
          Name of the image to build.