diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index d600075b..f7fdc23f 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -90,7 +90,7 @@ jobs:
   nix-master:
     strategy:
       matrix:
-        os: [ubuntu-latest, macos-latest]
+        os: [ubuntu-latest, macos-13]
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v4
diff --git a/test.nix b/test.nix
index 55bfcce7..667386cc 100644
--- a/test.nix
+++ b/test.nix
@@ -1,10 +1,10 @@
 # Realizes <num>> of derivations with size of <size>MB
 { size ? 1 # MB
-, num ? 10 # count 
+, num ? 10 # count
 , currentTime ? builtins.currentTime
 }:
 
-with (import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/21d8e70a69f704a6ab971b2d8265d40cc7bb69b1.tar.gz") {});
+with (import (fetchTarball "https://github.com/NixOS/nixpkgs/tarball/nixos-23.11") {});
 
 let
   drv = i: runCommand "${toString currentTime}-${toString i}" {} ''