diff --git a/index.d.ts b/index.d.ts
index 3a30112..ac80e5c 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -12,7 +12,8 @@ declare namespace classNames {
   type Value = string | number | boolean | undefined | null;
   type Mapping = Record<string, unknown>;
   interface ArgumentArray extends Array<Argument> {}
-  type Argument = Value | Mapping | ArgumentArray;
+  interface ReadonlyArgumentArray extends ReadonlyArray<Argument> {}
+  type Argument = Value | Mapping | ArgumentArray | ReadonlyArgumentArray;
 }
 
 interface ClassNames {
diff --git a/tests/types.ts b/tests/types.ts
index be8c2c0..b192580 100644
--- a/tests/types.ts
+++ b/tests/types.ts
@@ -20,6 +20,7 @@ classNames('bar', null, undefined, true, false, 1234);
 classNames('bar', ['abc', { foo: true }]);
 classNames('bar', ['abc', { foo: true }], { def: false, ijk: 1234 });
 classNames('abc', 1234, true, false, undefined, null, { foo: true }, ['abc', 1234, true, false, undefined, null, { foo: true }]);
+classNames('abc', 1234, true, false, undefined, null, { foo: true }, ['abc', 1234, true, false, undefined, null, { foo: true }], ['abc', 1234, true, false, undefined, null, { foo: true }] as const);
 // $ExpectError
 classNames(Symbol());
 // $ExpectError