diff --git a/module-options.nix b/module-options.nix
index c81ac33..fb989ef 100644
--- a/module-options.nix
+++ b/module-options.nix
@@ -23,6 +23,15 @@ let
 
   configFormat = pkgs.formats.toml { };
 
+  # Remove keys in the setting that are "empty" to keep the config file lean
+  emptySettingsKeys =
+    lib.optional (config.settings.excludes == []) "excludes"
+    ++ lib.optional (config.settings.on-unmatched == null) "on-unmatched";
+
+  settingsData = builtins.removeAttrs config.settings emptySettingsKeys;
+
+  configFile = configFormat.generate "treefmt.toml" settingsData;
+
   # The schema of the treefmt.toml data structure.
   configSchema = mkOption {
     default = { };
@@ -30,25 +39,23 @@ let
     type = types.submodule {
       freeformType = configFormat.type;
       options = {
-        global = {
-          excludes = mkOption {
-            description = "A global list of paths to exclude. Supports glob.";
-            type = types.listOf types.str;
-            default = [ ];
-            example = [ "./node_modules/**" ];
-          };
+        excludes = mkOption {
+          description = "A global list of paths to exclude. Supports glob.";
+          type = types.listOf types.str;
+          default = [ ];
+          example = [ "./node_modules/**" ];
+        };
 
-          on-unmatched = mkOption {
-            description = "Log paths that did not match any formatters at the specified log level.";
-            type = types.enum [
-              "debug"
-              "info"
-              "warn"
-              "error"
-              "fatal"
-            ];
-            default = "warn";
-          };
+        on-unmatched = mkOption {
+          description = "Log paths that did not match any formatters at the specified log level.";
+          type = types.nullOr (types.enum [
+            "debug"
+            "info"
+            "warn"
+            "error"
+            "fatal"
+          ]);
+          default = null;
         };
 
         formatter = mkOption {
@@ -276,7 +283,7 @@ in
 
   # Config
   config.build = {
-    configFile = configFormat.generate "treefmt.toml" config.settings;
+    inherit configFile;
     devShell = pkgs.mkShell {
       nativeBuildInputs = [ config.build.wrapper ] ++ (lib.attrValues config.build.programs);
     };