diff --git a/nix/coordinator.nix b/nix/coordinator.nix
index a75d315..fe17720 100644
--- a/nix/coordinator.nix
+++ b/nix/coordinator.nix
@@ -148,7 +148,7 @@ in
               outputs_path=${if cfg.outputsPath == null then "None" else builtins.toJSON cfg.outputsPath},
               prometheus_config=${if (!cfg.prometheus.enable) then "None" else builtins.toJSON {
                 inherit (cfg.prometheus) address port;
-              }}
+              }},
               # 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 {