diff --git a/index.d.ts b/index.d.ts
index 56491fa..2eaea05 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -2,9 +2,9 @@
 
 import sep from 'path';
 
-type AnymatchFn = (string:string) => boolean;
+type AnymatchFn = (string) => boolean;
 type AnymatchPattern = string|RegExp|AnymatchFn;
 type AnymatchMatcher = AnymatchPattern|Array<AnymatchPattern>
-declare function anymatch(matchers: AnymatchMatcher, testString: string, returnIndex?: boolean): boolean;
-declare function anymatch(matchers: AnymatchMatcher): (testString: string, returnIndex?: boolean) => number;
+declare function anymatch(matchers: AnymatchMatcher, testString: string|Array, returnIndex?: boolean): boolean;
+declare function anymatch(matchers: AnymatchMatcher): (testString: string|Array, returnIndex?: boolean) => number;
 export = anymatch;
\ No newline at end of file
diff --git a/index.js b/index.js
index 204f42a..623d161 100644
--- a/index.js
+++ b/index.js
@@ -67,9 +67,9 @@ const matchPatterns = (patterns, negatedGlobs, path, returnIndex) => {
 
 /**
  * @param {AnymatchMatcher} matchers
- * @param {String|Array<String>} testString
+ * @param {Array|string} testString
  * @param {Boolean=} returnIndex
- * @returns {boolean|Number|Function}
+ * @returns {boolean|number|Function}
  */
 const anymatch = (matchers, testString, returnIndex = false) => {
   if (matchers == null) {
diff --git a/test.js b/test.js
index 6a9f479..9106b31 100644
--- a/test.js
+++ b/test.js
@@ -105,26 +105,26 @@ describe('anymatch', () => {
 
     it('should pass extra args to function matchers', () => {
       matchers.push((string, arg1, arg2) => arg1 || arg2);
-      assert(!anymatch(matchers, 'bar.js'), 1);
-      assert(!anymatch(matchers, ['bar.js', 0]), 2);
-      assert(anymatch(matchers, ['bar.js', true]), 3);
-      assert(anymatch(matchers, ['bar.js', 0, true]), 4);
+      assert(!anymatch(matchers, 'bar.js'), '1');
+      assert(!anymatch(matchers, ['bar.js', 0]), '2');
+      assert(anymatch(matchers, ['bar.js', true]), '3');
+      assert(anymatch(matchers, ['bar.js', 0, true]), '4');
       // with returnIndex
-      assert.equal(anymatch(matchers, ['bar.js', 1], true), 4, 5);
+      assert.equal(anymatch(matchers, ['bar.js', 1], true), 4, '5');
       // curried versions
       var matchFn1 = anymatch(matchers);
       var matchFn2 = anymatch(matchers[4]);
-      assert(!matchFn1(['bar.js', 0]), 6);
-      assert(!matchFn2(['bar.js', 0]), 7);
-      assert(matchFn1(['bar.js', true]), 8);
-      assert(matchFn2(['bar.js', true]), 9);
-      assert(matchFn1(['bar.js', 0, true]), 10);
-      assert(matchFn2(['bar.js', 0, true]), 11);
+      assert(!matchFn1(['bar.js', 0]), '6');
+      assert(!matchFn2(['bar.js', 0]), '7');
+      assert(matchFn1(['bar.js', true]), '8');
+      assert(matchFn2(['bar.js', true]), '9');
+      assert(matchFn1(['bar.js', 0, true]), '10');
+      assert(matchFn2(['bar.js', 0, true]), '11');
       // curried with returnIndex
-      assert.equal(matchFn1(['bar.js', 1], true), 4, 12);
-      assert.equal(matchFn2(['bar.js', 1], true), 0, 13);
-      assert.equal(matchFn1(['bar.js', 0], true), -1, 14);
-      assert.equal(matchFn2(['bar.js', 0], true), -1, 15);
+      assert.equal(matchFn1(['bar.js', 1], true), 4, '12');
+      assert.equal(matchFn2(['bar.js', 1], true), 0, '13');
+      assert.equal(matchFn1(['bar.js', 0], true), -1, '14');
+      assert.equal(matchFn2(['bar.js', 0], true), -1, '15');
       matchers.pop();
     });
   });