diff --git a/flake.lock b/flake.lock
index 85a94807..0e4bf5fb 100644
--- a/flake.lock
+++ b/flake.lock
@@ -48,6 +48,44 @@
         "url": "https://gitea.c3d2.de/astro/heliwatch.git"
       }
     },
+    "hydra": {
+      "inputs": {
+        "newNixpkgs": "newNixpkgs",
+        "nix": "nix",
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1651520112,
+        "narHash": "sha256-LqBLIXYssvDoSp2Hf2+vDDB9O8VSF48HAGwL8pI2WZY=",
+        "owner": "nixos",
+        "repo": "hydra",
+        "rev": "7c133a98f8e689cdc13f8a1adaaa9cd75d039a35",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "repo": "hydra",
+        "type": "github"
+      }
+    },
+    "lowdown-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1633514407,
+        "narHash": "sha256-Dw32tiMjdK9t3ETl5fzGrutQTzh2rufgZV4A/BbxuD4=",
+        "owner": "kristapsdz",
+        "repo": "lowdown",
+        "rev": "d2c2b44ff6c27b936ec27358a2653caaef8f73b8",
+        "type": "github"
+      },
+      "original": {
+        "owner": "kristapsdz",
+        "repo": "lowdown",
+        "type": "github"
+      }
+    },
     "naersk": {
       "inputs": {
         "nixpkgs": [
@@ -68,6 +106,41 @@
         "type": "github"
       }
     },
+    "newNixpkgs": {
+      "locked": {
+        "lastModified": 1647380550,
+        "narHash": "sha256-909TI9poX7CIUiFx203WL29YON6m/I6k0ExbZvR7bLM=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "6e3ee8957637a60f5072e33d78e05c0f65c54366",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable-small",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nix": {
+      "inputs": {
+        "lowdown-src": "lowdown-src",
+        "nixpkgs": "nixpkgs",
+        "nixpkgs-regression": "nixpkgs-regression"
+      },
+      "locked": {
+        "lastModified": 1652280837,
+        "narHash": "sha256-N4To3tjnks/20pze4r1Wiu7s9+o21RxzKRfVX6+CDNo=",
+        "owner": "nixos",
+        "repo": "nix",
+        "rev": "b944b588fa280b0555b8269c0f6d097352f8716f",
+        "type": "github"
+      },
+      "original": {
+        "id": "nix",
+        "type": "indirect"
+      }
+    },
     "nixos-hardware": {
       "locked": {
         "lastModified": 1650522846,
@@ -85,18 +158,17 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1651368560,
-        "narHash": "sha256-OV6o5j27tnwqGhQd1u8/p5TjQI7+HyOnl6erteId4IE=",
-        "owner": "nixos",
+        "lastModified": 1645296114,
+        "narHash": "sha256-y53N7TyIkXsjMpOG7RhvqJFGDacLs9HlyHeSTBioqYU=",
+        "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "e41bd3eeadc4cab64f5de69f0c099058fa7d4127",
+        "rev": "530a53dcbc9437363471167a5e4762c5fcfa34a1",
         "type": "github"
       },
       "original": {
-        "owner": "nixos",
-        "ref": "release-21.11",
-        "repo": "nixpkgs",
-        "type": "github"
+        "id": "nixpkgs",
+        "ref": "nixos-21.05-small",
+        "type": "indirect"
       }
     },
     "nixpkgs-master": {
@@ -146,7 +218,38 @@
         "type": "github"
       }
     },
+    "nixpkgs-regression": {
+      "locked": {
+        "lastModified": 1643052045,
+        "narHash": "sha256-uGJ0VXIhWKGXxkeNnq4TvV3CIOkUJ3PAoLZ3HMzNVMw=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "215d4d0fd80ca5163643b03a33fde804a29cc1e2",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "rev": "215d4d0fd80ca5163643b03a33fde804a29cc1e2",
+        "type": "indirect"
+      }
+    },
     "nixpkgs_2": {
+      "locked": {
+        "lastModified": 1651368560,
+        "narHash": "sha256-OV6o5j27tnwqGhQd1u8/p5TjQI7+HyOnl6erteId4IE=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "e41bd3eeadc4cab64f5de69f0c099058fa7d4127",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "release-21.11",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs_3": {
       "locked": {
         "lastModified": 1651024496,
         "narHash": "sha256-uKSrrw/neSkxX6TXPSaMyfu7iKzFrK7F6HOt6vQefGY=",
@@ -179,7 +282,7 @@
     },
     "openwrt-imagebuilder": {
       "inputs": {
-        "nixpkgs": "nixpkgs_2",
+        "nixpkgs": "nixpkgs_3",
         "openwrt": "openwrt_2"
       },
       "locked": {
@@ -216,9 +319,10 @@
       "inputs": {
         "fenix": "fenix",
         "heliwatch": "heliwatch",
+        "hydra": "hydra",
         "naersk": "naersk",
         "nixos-hardware": "nixos-hardware",
-        "nixpkgs": "nixpkgs",
+        "nixpkgs": "nixpkgs_2",
         "nixpkgs-master": "nixpkgs-master",
         "nixpkgs-mobilizon": "nixpkgs-mobilizon",
         "nixpkgs-openwebrx": "nixpkgs-openwebrx",
diff --git a/flake.nix b/flake.nix
index a00c8d64..e24c8feb 100644
--- a/flake.nix
+++ b/flake.nix
@@ -51,6 +51,11 @@
     naersk.inputs.nixpkgs.follows = "nixpkgs";
     fenix.url = "github:nix-community/fenix";
     fenix.inputs.nixpkgs.follows = "nixpkgs";
+    hydra = {
+      url = "github:nixos/hydra";
+      inputs.nixpkgs.follows = "nixpkgs";
+      inputs.nix.url = "github:nixos/nix";
+    };
   };
 
   outputs = inputs@{ self, nixpkgs, secrets, nixos-hardware, zentralwerk, yammat, scrapers, spacemsg, tigger, ticker, heliwatch, sops-nix, naersk, fenix, ... }:
@@ -391,6 +396,7 @@
 
         hydra = nixosSystem' {
           modules = [
+            inputs.hydra.nixosModules.hydra
             ./hosts/hydra
             {
               sops.defaultSopsFile = "${secrets}/hosts/hydra/secrets.yaml";
diff --git a/hosts/hydra/cache.nix b/hosts/hydra/cache.nix
index 133905fb..312d8d97 100644
--- a/hosts/hydra/cache.nix
+++ b/hosts/hydra/cache.nix
@@ -23,4 +23,11 @@
     '';
   };
 
+  # workaround so that nix-serve builds with nix overriden by
+  # hydra.nixosModule
+  nixpkgs.config.packageOverrides = pkgs: {
+    nix-serve = pkgs.nix-serve.override {
+      nix = config.nix.package;
+    };
+  };
 }
diff --git a/hosts/hydra/hydra.nix b/hosts/hydra/hydra.nix
index c80570c5..89576588 100644
--- a/hosts/hydra/hydra.nix
+++ b/hosts/hydra/hydra.nix
@@ -23,20 +23,27 @@ in {
     daemonIOSchedPriority = 7;
   };
 
-  services.hydra = {
+  services.hydra-dev = {
     enable = true;
     hydraURL = "https://hydra.hq.c3d2.de";
     logo = ./c3d2.svg;
     notificationSender = "hydra@spam.works";
-    package = pkgs.hydra-unstable.overrideAttrs (oa: {
-      # HACK for Hydra error: cannot write modified lock file of flake
-      patchPhase = ''
-        ${pkgs.lib.optionalString (oa ? patchPhase) oa.patchPhase}
+    # package = pkgs.hydra-unstable.overrideAttrs (oa: {
+    #   src = pkgs.fetchFromGitHub {
+    #     owner = "nixos";
+    #     repo = "hydra";
+    #     # master as of 2022-05-02
+    #     rev = "7c133a98f8e689cdc13f8a1adaaa9cd75d039a35";
+    #     sha256 = "01mgg9ngpjinlwbgm2s287namilm3ddlwpn0hjs6267608vjgi02";
+    #   };
+    #   # HACK for Hydra error: cannot write modified lock file of flake
+    #   patchPhase = ''
+    #     ${pkgs.lib.optionalString (oa ? patchPhase) oa.patchPhase}
 
-        substituteInPlace src/script/hydra-eval-jobset \
-          --replace '"nix", "flake", "info"' '"nix", "flake", "info", "--no-write-lock-file"'
-      '';
-    });
+    #     substituteInPlace src/script/hydra-eval-jobset \
+    #       --replace '"nix", "flake", "info"' '"nix", "flake", "info", "--no-write-lock-file"'
+    #   '';
+    # });
     useSubstitutes = true;
     extraConfig = ''
       max_output_size = 4294967296