diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index ccfae256..6942de18 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -122,7 +122,10 @@ jobs:
 
       - uses: cachix/install-nix-action@v17
         with:
-          nix_path: nixpkgs=channel:nixos-25.05
+          nix_path: nixpkgs=channel:nixos-unstable:phps=https://github.com/fossar/nix-phps/archive/master.tar.gz
+          extra_nix_config: |
+            trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= fossar.cachix.org-1:Zv6FuqIboeHPWQS7ysLCJ7UT7xExb4OE8c4LyGb5AsE=
+            substituters = https://cache.nixos.org/ https://fossar.cachix.org
 
       - name: Run Unit Tests PHP8.1
         run: nix-shell --pure --run project-test-unit
diff --git a/shell.nix b/shell.nix
index 4319c0cd..07dadc0d 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,10 +1,14 @@
 {
   pkgs ? import <nixpkgs> { }
+  ,php81 ? import <phps>
   ,phpVersion ? "php81"
 }:
 
 let
-  php = pkgs.${phpVersion}.buildEnv {
+  phpVersionPkgs =
+    if (phpVersion == "php81") then php81.packages.x86_64-linux.${phpVersion}
+    else pkgs.${phpVersion};
+  php = phpVersionPkgs.buildEnv {
     extensions = { enabled, all }: enabled ++ (with all; [
       xdebug
     ]);
@@ -14,7 +18,7 @@ let
       memory_limit = 4G
     '';
   };
-  inherit(pkgs."${phpVersion}Packages") composer;
+  inherit(phpVersionPkgs.packages) composer;
 
   projectInstall = pkgs.writeShellApplication {
     name = "project-install";