diff --git a/images/capi/packer/azure/scripts/init-sig.sh b/images/capi/packer/azure/scripts/init-sig.sh
index 0591dc6902..587b193fc8 100755
--- a/images/capi/packer/azure/scripts/init-sig.sh
+++ b/images/capi/packer/azure/scripts/init-sig.sh
@@ -40,7 +40,7 @@ create_image_definition() {
   az sig image-definition create \
     --resource-group ${RESOURCE_GROUP_NAME} \
     --gallery-name ${GALLERY_NAME} \
-    --gallery-image-definition capi-${SIG_SKU:-$1} \
+    --gallery-image-definition ${SIG_IMAGE_DEFINITION:-capi-${SIG_SKU:-$1}} \
     --publisher ${SIG_PUBLISHER:-capz} \
     --offer ${SIG_OFFER:-capz-demo} \
     --sku ${SIG_SKU:-$2} \