diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 9bf5a02..43aa0f5 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -17,9 +17,10 @@ stages:
   - debian-package
 
 .image-buster:
-  IMAGE_NAME: pkg_build-exim-encrypt-dlfunc/buster
-  BUILD_FILE: Dockerfile.buster
-  TARGET_REPOSITORY: "buster"
+  variables:
+    IMAGE_NAME: pkg_build-exim-encrypt-dlfunc/buster
+    BUILD_FILE: Dockerfile.buster
+    TARGET_REPOSITORY: "buster"
 
 .image-bullseye:
   IMAGE_NAME: pkg_build-exim-encrypt-dlfunc/bullseye