diff --git a/index.d.ts b/index.d.ts
index 84650b6..fa4b910 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,19 +1,22 @@
 declare const unusedFilename: {
 	/**
-	 * Get an unused filename by appending a number if it exists: `file.txt` → `file (1).txt`.
-	 *
-	 * @param filePath - The path to check for filename collision.
-	 * @returns Either the original `filename` or the `filename` appended with a number.
-	 */
+	Get an unused filename by appending a number if it exists: `file.txt` → `file (1).txt`.
+
+	@param filePath - The path to check for filename collision.
+	@returns Either the original `filename` or the `filename` appended with a number.
+	*/
 	(filePath: string): Promise<string>;
 
 	/**
-	 * Synchronously get an unused filename by appending a number if it exists: `file.txt` → `file (1).txt`.
-	 *
-	 * @param filePath - The path to check for filename collision.
-	 * @returns Either the original `filename` or the `filename` appended with a number.
-	 */
+	Synchronously get an unused filename by appending a number if it exists: `file.txt` → `file (1).txt`.
+
+	@param filePath - The path to check for filename collision.
+	@returns Either the original `filename` or the `filename` appended with a number.
+	*/
 	sync(filePath: string): string;
-}
 
-export default unusedFilename;
+	// TODO: Remove this for the next major release
+	default: typeof unusedFilename;
+};
+
+export = unusedFilename;
diff --git a/index.js b/index.js
index e26dc09..f8f8c10 100644
--- a/index.js
+++ b/index.js
@@ -14,6 +14,7 @@ const unusedFilename = filePath => {
 };
 
 module.exports = unusedFilename;
+// TODO: Remove this for the next major release
 module.exports.default = unusedFilename;
 
 module.exports.sync = filePath => {
diff --git a/index.test-d.ts b/index.test-d.ts
index 164b5f4..f87a178 100644
--- a/index.test-d.ts
+++ b/index.test-d.ts
@@ -1,5 +1,5 @@
-import {expectType} from 'tsd-check';
-import unusedFilename from '.';
+import {expectType} from 'tsd';
+import unusedFilename = require('.');
 
 expectType<Promise<string>>(unusedFilename('rainbow.txt'));
 expectType<string>(unusedFilename.sync('rainbow.txt'));
diff --git a/package.json b/package.json
index a1bf7cd..06d87cf 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,7 @@
 		"node": ">=8"
 	},
 	"scripts": {
-		"test": "xo && ava && tsd-check"
+		"test": "xo && ava && tsd"
 	},
 	"files": [
 		"index.js",
@@ -36,11 +36,11 @@
 	],
 	"dependencies": {
 		"modify-filename": "^1.1.0",
-		"path-exists": "^3.0.0"
+		"path-exists": "^4.0.0"
 	},
 	"devDependencies": {
-		"ava": "^1.3.1",
-		"tsd-check": "^0.3.0",
+		"ava": "^1.4.1",
+		"tsd": "^0.7.2",
 		"xo": "^0.24.0"
 	}
 }