diff --git a/pkgs/development/tools/misc/hydra/default.nix b/pkgs/development/tools/misc/hydra/default.nix
deleted file mode 100644
index 5289015d43b..00000000000
--- a/pkgs/development/tools/misc/hydra/default.nix
+++ /dev/null
@@ -1,26 +0,0 @@
-{ lib, fetchFromGitHub, callPackage, nixVersions, nixosTests, fetchpatch }:
-
-{
-  hydra-unstable = callPackage ./common.nix {
-    version = "2022-02-07";
-    src = fetchFromGitHub {
-      owner = "NixOS";
-      repo = "hydra";
-      rev = "517dce285a851efd732affc084c7083aed2e98cd";
-      sha256 = "sha256-abWhd/VLNse3Gz7gcVbFANJLAhHV4nbOKjhVDmq/Zmg=";
-    };
-    patches = [
-      ./eval.patch
-      ./missing-std-string.patch
-      (fetchpatch {
-        url = "https://github.com/NixOS/hydra/commit/5ae26aa7604f714dcc73edcb74fe71ddc8957f6c.patch";
-        sha256 = "sha256-wkbWo8SFbT3qwVxwkKQWpQT5Jgb1Bb51yiLTlFdDN/I=";
-      })
-    ];
-    nix = nixVersions.nix_2_6;
-
-    tests = {
-      basic = nixosTests.hydra.hydra-unstable;
-    };
-  };
-}
diff --git a/pkgs/development/tools/misc/hydra/common.nix b/pkgs/development/tools/misc/hydra/unstable.nix
similarity index 84%
rename from pkgs/development/tools/misc/hydra/common.nix
rename to pkgs/development/tools/misc/hydra/unstable.nix
index 2314f5f9f64..7d3521702a7 100644
--- a/pkgs/development/tools/misc/hydra/common.nix
+++ b/pkgs/development/tools/misc/hydra/unstable.nix
@@ -1,16 +1,20 @@
-{ stdenv, nix, perlPackages, buildEnv
+{ stdenv
+, lib
+, nix, perlPackages, buildEnv
 , makeWrapper, autoconf, automake, libtool, unzip, pkg-config, sqlite, libpqxx_6
 , top-git, mercurial, darcs, subversion, breezy, openssl, bzip2, libxslt
 , perl, postgresql, nukeReferences, git, boehmgc, nlohmann_json
 , docbook_xsl, openssh, gnused, coreutils, findutils, gzip, xz, gnutar
-, rpm, dpkg, cdrkit, pixz, lib, boost, autoreconfHook, src ? null, version ? null
-, migration ? false, patches ? []
-, tests ? {}, mdbook
+, rpm, dpkg, cdrkit, pixz, boost, autoreconfHook
+, mdbook
 , foreman
 , python3
 , libressl
 , cacert
 , glibcLocales
+, fetchFromGitHub
+, fetchpatch
+, nixosTests
 }:
 
 let
@@ -88,8 +92,14 @@ let
   };
 in stdenv.mkDerivation rec {
   pname = "hydra";
+  version = "2022-02-07";
 
-  inherit stdenv src version patches;
+  src = fetchFromGitHub {
+    owner = "NixOS";
+    repo = "hydra";
+    rev = "517dce285a851efd732affc084c7083aed2e98cd";
+    sha256 = "sha256-abWhd/VLNse3Gz7gcVbFANJLAhHV4nbOKjhVDmq/Zmg=";
+  };
 
   buildInputs =
     [ makeWrapper libtool unzip nukeReferences sqlite libpqxx_6
@@ -116,6 +126,15 @@ in stdenv.mkDerivation rec {
     libressl.nc
   ];
 
+  patches = [
+    ./eval.patch
+    ./missing-std-string.patch
+    (fetchpatch {
+      url = "https://github.com/NixOS/hydra/commit/5ae26aa7604f714dcc73edcb74fe71ddc8957f6c.patch";
+      sha256 = "sha256-wkbWo8SFbT3qwVxwkKQWpQT5Jgb1Bb51yiLTlFdDN/I=";
+    })
+  ];
+
   configureFlags = [ "--with-docbook-xsl=${docbook_xsl}/xml/xsl/docbook" ];
 
   NIX_CFLAGS_COMPILE = "-pthread";
@@ -152,7 +171,10 @@ in stdenv.mkDerivation rec {
 
   doCheck = true;
 
-  passthru = { inherit perlDeps migration tests; };
+  passthru = {
+    inherit perlDeps;
+    tests.basic = nixosTests.hydra.hydra-unstable;
+  };
 
   meta = with lib; {
     description = "Nix-based continuous build system";
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 8f432f8e438..e98ae93e1fc 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -17830,8 +17830,7 @@ with pkgs;
 
   hwloc = callPackage ../development/libraries/hwloc {};
 
-  inherit (callPackage ../development/tools/misc/hydra { })
-    hydra-unstable;
+  hydra-unstable = callPackage ../development/tools/misc/hydra/unstable.nix { nix = nixVersions.nix_2_6; };
 
   hydra-cli = callPackage ../development/tools/misc/hydra-cli { };