diff --git a/machines/agate/default.nix b/machines/agate/default.nix
index e626b76..abe5dfa 100644
--- a/machines/agate/default.nix
+++ b/machines/agate/default.nix
@@ -43,8 +43,12 @@
   nix.settings = {
     max-jobs = 8;
     cores = 16;
+    substituters = [ "https://cache.ngi0.nixos.org/" ];
+    trusted-public-keys = [ "cache.ngi0.nixos.org-1:KqH5CBLNSyX184S9BKZJo1LxrxJ9ltnY2uAs5c/f1MA=" ];
   };
 
+  nixpkgs.config.contentAddressedByDefault = true;
+
   services.tailscale = {
     enable = true;
     openFirewall = true;
diff --git a/machines/agate/services/hydra.nix b/machines/agate/services/hydra.nix
index 3f95483..6d3df20 100644
--- a/machines/agate/services/hydra.nix
+++ b/machines/agate/services/hydra.nix
@@ -4,5 +4,6 @@
     hydraURL = "http://agate.coho-tet.ts.net:3000/";
     notificationSender = "hydra@localhost";
     buildMachinesFiles = [ ];
+    useSubstitutes = true;
   };
 }
diff --git a/modules/nixos/common-settings/nix-conf.nix b/modules/nixos/common-settings/nix-conf.nix
index f6a7684..e28e899 100644
--- a/modules/nixos/common-settings/nix-conf.nix
+++ b/modules/nixos/common-settings/nix-conf.nix
@@ -47,6 +47,7 @@ in
       experimental-features = [
         "nix-command"
         "flakes"
+        "ca-derivations"
       ];
       auto-optimise-store = true;
       trusted-users = [ "root" ];