diff --git a/.gitattributes b/.gitattributes
index 391f0a4..6313b56 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,2 +1 @@
-* text=auto
-*.js text eol=lf
+* text=auto eol=lf
diff --git a/.travis.yml b/.travis.yml
index e0cc348..2ae9d62 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,4 +1,5 @@
 language: node_js
 node_js:
+  - '10'
   - '8'
   - '6'
diff --git a/index.d.ts b/index.d.ts
new file mode 100644
index 0000000..02d9581
--- /dev/null
+++ b/index.d.ts
@@ -0,0 +1,20 @@
+/**
+Generate random numbers that are consecutively unique.
+
+@returns A function that when called will return a random number that is never the same as the previous.
+
+@example
+```
+import uniqueRandom = require('unique-random');
+const random = uniqueRandom(1, 10);
+
+console.log(random(), random(), random());
+//=> 5 2 6
+```
+*/
+declare function uniqueRandom(
+	minimum: number,
+	maximum: number
+): () => number;
+
+export = uniqueRandom;
diff --git a/index.js b/index.js
index e8e8916..ba4a188 100644
--- a/index.js
+++ b/index.js
@@ -1,9 +1,12 @@
 'use strict';
-module.exports = (min, max) => {
-	let prev;
-	return function rand() {
-		const num = Math.floor((Math.random() * (max - min + 1)) + min);
-		prev = (num === prev && min !== max) ? rand() : num;
-		return prev;
+
+module.exports = (minimum, maximum) => {
+	let previousValue;
+	return function random() {
+		const number = Math.floor(
+			(Math.random() * (maximum - minimum + 1)) + minimum
+		);
+		previousValue = number === previousValue && minimum !== maximum ? random() : number;
+		return previousValue;
 	};
 };
diff --git a/index.test-d.ts b/index.test-d.ts
new file mode 100644
index 0000000..639ff61
--- /dev/null
+++ b/index.test-d.ts
@@ -0,0 +1,7 @@
+import {expectType} from 'tsd';
+import uniqueRandom = require('.');
+
+const random = uniqueRandom(1, 10);
+
+expectType<() => number>(random);
+expectType<number>(random());
diff --git a/package.json b/package.json
index 739605f..ead494d 100644
--- a/package.json
+++ b/package.json
@@ -13,10 +13,11 @@
 		"node": ">=6"
 	},
 	"scripts": {
-		"test": "xo && ava"
+		"test": "xo && ava && tsd"
 	},
 	"files": [
-		"index.js"
+		"index.js",
+		"index.d.ts"
 	],
 	"keywords": [
 		"unique",
@@ -30,7 +31,8 @@
 		"consecutively"
 	],
 	"devDependencies": {
-		"ava": "*",
-		"xo": "*"
+		"ava": "^1.4.1",
+		"tsd": "^0.7.2",
+		"xo": "^0.24.0"
 	}
 }
diff --git a/readme.md b/readme.md
index fa13553..e42bc39 100644
--- a/readme.md
+++ b/readme.md
@@ -16,16 +16,16 @@ $ npm install unique-random
 
 ```js
 const uniqueRandom = require('unique-random');
-const rand = uniqueRandom(1, 10);
+const random = uniqueRandom(1, 10);
 
-console.log(rand(), rand(), rand());
+console.log(random(), random(), random());
 //=> 5 2 6
 ```
 
 
 ## API
 
-### uniqueRandom(min, max)
+### uniqueRandom(minimum, maximum)
 
 Returns a function that when called will return a random number that is never the same as the previous.
 
diff --git a/test.js b/test.js
index d775302..9c0e4ab 100644
--- a/test.js
+++ b/test.js
@@ -1,20 +1,24 @@
 import test from 'ava';
-import m from '.';
+import uniqueRandom from '.';
 
 test('main', t => {
-	const uniqueRandom = m(1, 10);
+	const random = uniqueRandom(1, 10);
 	let count = 1000;
-	let current;
-	let prev;
+	let currentValue;
+	let previousValue;
 
 	while (--count > 0) {
-		current = uniqueRandom();
+		currentValue = random();
 
-		if (current === prev || current > 10 || current < 1) {
+		if (
+			currentValue === previousValue ||
+			currentValue > 10 ||
+			currentValue < 1
+		) {
 			t.fail();
 		}
 
-		prev = current;
+		previousValue = currentValue;
 	}
 
 	t.pass();