diff --git a/base.js b/base.js
index ca0477f..91e9891 100644
--- a/base.js
+++ b/base.js
@@ -19,6 +19,13 @@ module.exports = {
       rules: {
         // https://typescript-eslint.io/rules/
 
+        '@typescript-eslint/array-type': [
+          'error',
+          {
+            default: 'array-simple',
+            readonly: 'array-simple',
+          },
+        ],
         // Too noisy for now.
         '@typescript-eslint/no-confusing-void-expression': 'off',
         // Empty interfaces are common (React component props that extend others, AdonisJS default configs).
diff --git a/test/notOk.ts b/test/notOk.ts
index ebafda3..5c610ff 100644
--- a/test/notOk.ts
+++ b/test/notOk.ts
@@ -5,3 +5,9 @@ function testX(x: number) {
 }
 
 testX(x!);
+
+function testY(y: (number | string)[]) {
+  return y;
+}
+
+testY([1, 2, 3, '4']);
diff --git a/test/ok.ts b/test/ok.ts
index 3abcd3f..007cff6 100644
--- a/test/ok.ts
+++ b/test/ok.ts
@@ -7,11 +7,11 @@ export interface X {
  * @param x - This is a x.
  * @returns The best number in the world.
  */
-function test(x: number) {
-  return x + 42;
+function test(x: readonly number[]) {
+  return x[0] + 42;
 }
 
-test(1);
+test([1]);
 
 /**
  * Logs 42.
diff --git a/test/test.mjs b/test/test.mjs
index 7e553e7..3fab194 100644
--- a/test/test.mjs
+++ b/test/test.mjs
@@ -26,6 +26,7 @@ const errors = notOkResult.messages
   .map((error) => error.ruleId)
   .sort();
 assert.deepStrictEqual(errors, [
+  '@typescript-eslint/array-type',
   '@typescript-eslint/no-non-null-assertion',
   '@typescript-eslint/no-unnecessary-type-assertion',
 ]);