diff --git a/debian/gitlab-ci.yml b/debian/gitlab-ci.yml
index 22cc5541b1d65d3d9dddcd41de02c0267efd0204..6cb00c9fe9300ac950ac123ca013b941058af3d1 100644
--- a/debian/gitlab-ci.yml
+++ b/debian/gitlab-ci.yml
@@ -423,11 +423,11 @@ test:debian-13:
 
 test:ubuntu-18.04:
     extends: .test_deb
-    image: ubuntu:18.04
+    image: ${CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX}/ubuntu:18.04
 
 test:ubuntu-20.04:
     extends: .test_deb
-    image: ubuntu:20.04
+    image: ${CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX}/ubuntu:20.04
 
 test:archlinux:
     extends: .test_template