diff --git a/pkgs/by-name/ni/nixos-rebuild-ng/package.nix b/pkgs/by-name/ni/nixos-rebuild-ng/package.nix
index df33313193fe..02e140fcc0a6 100644
--- a/pkgs/by-name/ni/nixos-rebuild-ng/package.nix
+++ b/pkgs/by-name/ni/nixos-rebuild-ng/package.nix
@@ -89,6 +89,7 @@ python3Packages.buildPythonApplication rec {
         ps: with ps; [
           mypy
           pytest
+          pytest-mock
           ruff
         ]
       );