diff --git a/nixos/modules/build.nix b/nixos/modules/build.nix
index 0794c6e..76001e7 100644
--- a/nixos/modules/build.nix
+++ b/nixos/modules/build.nix
@@ -64,10 +64,10 @@ let
                 ip = "${iproute2}/bin/ip";
                 nbd-client = "${nbd}/bin/nbd-client";
               };
-              extraConfig = ''
-                DefaultTimeoutStartSec=20
-                DefaultDeviceTimeoutSec=20
-              '';
+              settings.Manager = {
+                DefaultTimeoutStartSec = "20s";
+                DefaultDeviceTimeoutSec = "20s";
+              };
 
               network = {
                 enable = true;