diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 702c294..b72b9f9 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -3,11 +3,11 @@ hydra-pr:
     - merge_requests
   image: nixos/nix
   script:
-    - nix-shell -I nixpkgs=channel:nixos-unstable -p hydra-cli --run 'hydra-cli -H https://hydra.nix-community.org jobset-wait simple-nixos-mailserver ${CI_MERGE_REQUEST_IID}'
+    - nix-shell -I nixpkgs=channel:nixos-22.05 -p hydra-cli --run 'hydra-cli -H https://hydra.nix-community.org jobset-wait simple-nixos-mailserver ${CI_MERGE_REQUEST_IID}'
 
 hydra-master:
   only:
     - master
   image: nixos/nix
   script:
-    - nix-shell -I nixpkgs=channel:nixos-unstable -p hydra-cli --run 'hydra-cli -H https://hydra.nix-community.org jobset-wait simple-nixos-mailserver master'
+    - nix-shell -I nixpkgs=channel:nixos-22.05 -p hydra-cli --run 'hydra-cli -H https://hydra.nix-community.org jobset-wait simple-nixos-mailserver master'