diff --git a/nix/coordinator.nix b/nix/coordinator.nix
index 5459713..82b3ee5 100644
--- a/nix/coordinator.nix
+++ b/nix/coordinator.nix
@@ -5,6 +5,7 @@
 , ...
 }:
 let
+  inherit (lib) filterAttrs;
   cfg = config.services.buildbot-nix.coordinator;
 in
 {
@@ -246,7 +247,7 @@ in
               prometheus_config=${if (!cfg.prometheus.enable) then "None" else builtins.toJSON {
                 inherit (cfg.prometheus) address port;
               }},
-              nix_builders=${builtins.toJSON cfg.buildMachines},
+              nix_builders=${builtins.toJSON (map (b: filterAttrs (n: _: n != "system") b) cfg.buildMachines)},
               # Signing key file must be available on the workers and readable.
               signing_keyfile=${if cfg.signingKeyFile == null then "None" else builtins.toJSON cfg.signingKeyFile},
               binary_cache_config=${if (!cfg.binaryCache.enable) then "None" else builtins.toJSON {