diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index bff742c..e8c146c 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -55,3 +55,5 @@ stages:
 - build-images
 - build
 - trigger
+variables:
+  NIX_CI_IMAGE: $CI_REGISTRY_IMAGE/nix-ci:$CI_COMMIT_SHORT_SHA
diff --git a/nix/repo/ci.nix b/nix/repo/ci.nix
index a76c0d8..157ede7 100644
--- a/nix/repo/ci.nix
+++ b/nix/repo/ci.nix
@@ -10,6 +10,7 @@ in
       # the child pipeline can then use the built images to test them
       extraData = {
         stages = ["build-images" "build" "trigger"];
+        variables.NIX_CI_IMAGE = "$CI_REGISTRY_IMAGE/nix-ci:$CI_COMMIT_SHORT_SHA";
         "build:image" = {
           stage = "build-images";
           parallel.matrix = [