diff --git a/nix/hosts/default.nix b/nix/hosts/default.nix
index 8df02f2..fc7eeaa 100644
--- a/nix/hosts/default.nix
+++ b/nix/hosts/default.nix
@@ -132,7 +132,32 @@ in
   # nix-darwin configurations
   flake.darwinConfigurations = mkDarwinConfigurations {
     eR17 = { };
-    eR17x = { };
+    eR17x = {
+      modules = [
+        {
+          nix.settings.builders-use-substitutes = true;
+          nix.linux-builder = {
+            enable = true;
+            ephemeral = true;
+            maxJobs = 4;
+            config = {
+              virtualisation = {
+                darwin-builder = {
+                  diskSize = 40 * 1024;
+                  memorySize = 8 * 1024;
+                };
+                cores = 6;
+              };
+              nix.settings.sandbox = false;
+              users.users.root.openssh.authorizedKeys.keys = [
+                "ssh-rsa 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"
+              ];
+            };
+          };
+          nix.settings.trusted-users = [ "@admin" ];
+        }
+      ];
+    };
   };
 
   flake.nixOnDroidConfigurations.default = mkDroidConfiguration rec {
diff --git a/nix/nix.nix b/nix/nix.nix
index 03b420a..574977a 100644
--- a/nix/nix.nix
+++ b/nix/nix.nix
@@ -26,7 +26,6 @@ in
       nix-path = nixPath;
       auto-optimise-store = true;
       accept-flake-config = true;
-      builders-use-substitutes = false;
       download-attempts = 3;
       fallback = true;
       http-connections = 0;