diff --git a/index.d.ts b/index.d.ts
index 6b7aaac..c72a414 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,24 +1,65 @@
-export interface Options {
-	/**
-	 * Use a key distance-based score to leniently accept typos of `yes` and `no`.
-	 *
-	 * @default false
-	 */
-	lenient?: boolean;
+declare namespace yn {
+	interface Options {
+		/**
+		Use a key distance-based score to leniently accept typos of `yes` and `no`.
 
-	/**
-	 * Default value if no match was found.
-	 *
-	 * @default null
-	 */
-	default?: boolean | null;
+		@default false
+		*/
+		readonly lenient?: boolean;
+
+		/**
+		Default value if no match was found.
+
+		@default null
+		*/
+		readonly default?: boolean | null;
+	}
+
+	interface OptionsWithDefault extends Options {
+		default: boolean;
+	}
 }
 
-/**
- * Parse yes/no like values.
- * The following case-insensitive values are recognized: `'y', 'yes', 'true', true, '1', 1, 'n', 'no', 'false', false, '0', 0`
- *
- * @param input - Value that should be converted.
- * @returns The parsed input if it can be parsed or the default value defined in the `default` option.
- */
-export default function yn(input: any, options?: Options): boolean | null;
+declare const yn: {
+	/**
+	Parse yes/no like values.
+
+	The following case-insensitive values are recognized: `'y', 'yes', 'true', true, '1', 1, 'n', 'no', 'false', false, '0', 0`
+
+	@param input - Value that should be converted.
+	@returns The parsed input if it can be parsed or the default value defined in the `default` option.
+
+	@example
+	```
+	import yn = require('yn');
+
+	yn('y');
+	//=> true
+
+	yn('NO');
+	//=> false
+
+	yn(true);
+	//=> true
+
+	yn('abomasum');
+	//=> null
+
+	yn('abomasum', {default: false});
+	//=> false
+
+	yn('mo', {lenient: true});
+	//=> false
+	```
+	*/
+	(input: unknown, options: yn.OptionsWithDefault): boolean;
+	(input: unknown, options?: yn.Options): boolean | null;
+
+	// TODO: Remove this for the next major release, refactor the whole definition to:
+	// declare function yn(input: unknown, options: yn.OptionsWithDefault): boolean;
+	// declare function yn(input: unknown, options?: yn.Options): boolean | null;
+	// export = yn;
+	default: typeof yn;
+};
+
+export = yn;
diff --git a/index.js b/index.js
index fd91d63..a5a24c1 100644
--- a/index.js
+++ b/index.js
@@ -29,4 +29,5 @@ const yn = (input, options) => {
 };
 
 module.exports = yn;
+// TODO: Remove this for the next major release
 module.exports.default = yn;
diff --git a/index.test-d.ts b/index.test-d.ts
index 339ef3b..220701d 100644
--- a/index.test-d.ts
+++ b/index.test-d.ts
@@ -1,11 +1,6 @@
-import {expectType} from 'tsd-check';
-import yn from '.';
+import {expectType} from 'tsd';
+import yn = require('.');
 
-// Should use null as default when no options are given
-expectType<boolean | null>(yn('true'));
-
-// Should use the default type when given
-expectType<boolean | null>(yn('true', {default: null}));
-
-// Should use null as default when only the lenient option is given
-expectType<boolean | null>(yn('true', {lenient: true}));
+expectType<boolean | null>(yn('y'));
+expectType<boolean | null>(yn('mo', {lenient: true}));
+expectType<boolean>(yn('abomasum', {default: false}));
diff --git a/package.json b/package.json
index 933384e..b08b4d6 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,7 @@
 		"node": ">=6"
 	},
 	"scripts": {
-		"test": "xo && ava && tsd-check"
+		"test": "xo && ava && tsd"
 	},
 	"files": [
 		"index.js",
@@ -35,8 +35,8 @@
 		"lenient"
 	],
 	"devDependencies": {
-		"ava": "^0.25.0",
-		"tsd-check": "^0.2.1",
-		"xo": "^0.23.0"
+		"ava": "^1.4.1",
+		"tsd": "^0.7.2",
+		"xo": "^0.24.0"
 	}
 }