diff --git a/index.d.ts b/index.d.ts
index d85babf..b565538 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -1,8 +1,13 @@
 import * as React from 'react';
 
-export function autoBind(el: React.ReactNode, options?: any): React.ReactNode;
+interface AutoBindOptions {
+	include?: Array<string | RegExp>
+	exclude?: Array<string | RegExp>
+}
+
+export function autoBind(element: React.ReactNode, options?: AutoBindOptions): React.ReactNode;
 
-export function classNames(...args: any[]): string;
+export function classNames(...args: Array<string | {[key: string]: unknown}>): string;
 
 export function isStatelessComponent(component: React.ComponentClass): boolean;
 
@@ -31,8 +36,8 @@ export class Choose extends React.Component {
 }
 
 interface ForProps {
-	of: any[];
-	render?: (item: any, index: number) => React.ReactNode;
+	of: unknown[];
+	render?: (item: unknown, index: number) => React.ReactNode;
 }
 
 export class For extends React.Component<ForProps> {}
diff --git a/index.test-d.ts b/index.test-d.ts
new file mode 100644
index 0000000..41a8880
--- /dev/null
+++ b/index.test-d.ts
@@ -0,0 +1,4 @@
+import {expectType} from 'tsd-check';
+import {classNames} from '.';
+
+expectType<string>(classNames('foo', {bar: true}));
diff --git a/package.json b/package.json
index 9b7c1e4..0e49f56 100644
--- a/package.json
+++ b/package.json
@@ -15,7 +15,7 @@
 	},
 	"scripts": {
 		"build": "babel index.js auto-bind.js class-names.js --out-dir=dist",
-		"test": "xo && ava",
+		"test": "xo && ava && tsd-check",
 		"prepublishOnly": "npm run build"
 	},
 	"files": [
@@ -58,6 +58,7 @@
 		"react": "^16.7.0",
 		"react-dom": "^16.7.0",
 		"react-test-renderer": "^16.7.0",
+		"tsd-check": "^0.3.0",
 		"xo": "^0.23.0"
 	},
 	"peerDependencies": {