diff --git a/index.js b/index.js
index 4459afd..2c549e4 100644
--- a/index.js
+++ b/index.js
@@ -11,9 +11,12 @@
  * Results cache
  */
 
+var isNumber = require('is-number');
 var res = '';
 var cache;
 
+
+
 /**
  * Expose `repeat`
  */
@@ -38,16 +41,39 @@ module.exports = repeat;
  * @api public
  */
 
+function isInt(input){
+  if(!isNumber(input)){
+    throw new TypeError("input must be a number. Your input was " + typeof input);
+  }else{
+    return (input % 1) === 0;
+  }
+}
+
+//prototype modification to allow node v0.10.0 to have access to the isInteger function.
+if(! Number.isInteger){
+  Number.isInteger = isInt;
+}
+
 function repeat(str, num) {
   if (typeof str !== 'string') {
     throw new TypeError('expected a string');
   }
+  
+  // cover null or undefined cases
+  if (num === null || num === undefined) {
+    return "";
+  }
+
+  if (!(isNumber(num) && Number.isInteger(typeof num !== 'string' ? num : Number(num)) && num >= 0)) {
+    throw new TypeError('expected a positive integer number ');
+  }
 
   // cover common, quick use cases
   if (num === 1) return str;
   if (num === 2) return str + str;
+  if (num === 0) return "";
 
-  var max = str.length * num;
+  var max = str.length * num;  
   if (cache !== str || typeof cache === 'undefined') {
     cache = str;
     res = '';
diff --git a/package.json b/package.json
index fc0d190..602a3bf 100644
--- a/package.json
+++ b/package.json
@@ -9,7 +9,8 @@
     "Jon Schlinkert <jon.schlinkert@sellside.com> (http://twitter.com/jonschlinkert)",
     "Linus Unnebäck <linus@folkdatorn.se> (http://linus.unnebäck.se)",
     "Thijs Busser <tbusser@gmail.com> (http://tbusser.net)",
-    "Titus <tituswormer@gmail.com> (wooorm.com)"
+    "Titus <tituswormer@gmail.com> (wooorm.com)",
+    "ggattoni (https://github.com/ggattoni)"
   ],
   "repository": "jonschlinkert/repeat-string",
   "bugs": {
@@ -26,6 +27,9 @@
   "scripts": {
     "test": "mocha"
   },
+  "dependencies" : {
+    "is-number" : "^6.0.0"
+  },
   "devDependencies": {
     "ansi-cyan": "^0.1.1",
     "benchmarked": "^0.2.5",
@@ -74,4 +78,4 @@
       "verb"
     ]
   }
-}
\ No newline at end of file
+}