diff --git a/lib/options-manager.js b/lib/options-manager.js
index 9df909ce..c275914f 100644
--- a/lib/options-manager.js
+++ b/lib/options-manager.js
@@ -129,7 +129,7 @@ const mergeWithFileConfig = async options => {
 		options.ts = true;
 		const config = makeTSConfig(tsConfig, tsConfigPath, [options.filePath]);
 		await fs.mkdir(path.dirname(options.tsConfigPath), {recursive: true});
-		await fs.writeFile(options.tsConfigPath, JSON.stringify(config), 'utf8');
+		await fs.writeFile(options.tsConfigPath, JSON.stringify(config));
 	}
 
 	return {options, prettierOptions};
diff --git a/test/options-manager.js b/test/options-manager.js
index efc632d3..d66bc5c1 100644
--- a/test/options-manager.js
+++ b/test/options-manager.js
@@ -557,7 +557,7 @@ test('mergeWithFileConfig: typescript files', async t => {
 	const expectedConfigPath = new RegExp(`${slash(cwd)}/node_modules/.cache/xo-linter/tsconfig\\..*\\.json[\\/]?$`, 'u');
 	t.regex(slash(options.tsConfigPath), expectedConfigPath);
 	t.deepEqual(omit(options, 'tsConfigPath'), expected);
-	t.deepEqual(JSON.parse(await fs.readFile(options.tsConfigPath, 'utf8')), {
+	t.deepEqual(JSON.parse(await fs.readFile(options.tsConfigPath)), {
 		extends: path.resolve(cwd, 'tsconfig.json'),
 		files: [path.resolve(cwd, 'file.ts')],
 		include: [slash(path.resolve(cwd, '**/*.ts')), slash(path.resolve(cwd, '**/*.tsx'))],
@@ -579,7 +579,7 @@ test('mergeWithFileConfig: tsx files', async t => {
 	const expectedConfigPath = new RegExp(`${slash(cwd)}/node_modules/.cache/xo-linter/tsconfig\\..*\\.json[\\/]?$`, 'u');
 	t.regex(slash(options.tsConfigPath), expectedConfigPath);
 	t.deepEqual(omit(options, 'tsConfigPath'), expected);
-	t.deepEqual(JSON.parse(await fs.readFile(options.tsConfigPath, 'utf8')), {
+	t.deepEqual(JSON.parse(await fs.readFile(options.tsConfigPath)), {
 		extends: path.resolve(cwd, 'tsconfig.json'),
 		files: [path.resolve(cwd, 'file.tsx')],
 		include: [slash(path.resolve(cwd, '**/*.ts')), slash(path.resolve(cwd, '**/*.tsx'))],