diff --git a/myanmar-phonenumber.js b/myanmar-phonenumber.js
index df08f91..6b5c320 100644
--- a/myanmar-phonenumber.js
+++ b/myanmar-phonenumber.js
@@ -43,14 +43,14 @@
 
     // Removes trailing spaces, dashes and double country codes
     myanmarPhoneNumber.sanitizeInput = function (phoneNumber) {
+      if (!phoneNumber) {
+        throw Error('Please include phoneNumber parameter.');
+      }
+
       phoneNumber = phoneNumber.trim();
 
       if (phoneNumber.length === 0) {
-        return new Error('Phone number is empty.');
-      }
-
-      if (!phoneNumber) {
-        return new Error('Please include phoneNumber parameter.');
+        throw Error('Phone number is empty.');
       }
 
       phoneNumber = phoneNumber.replace(/[- )(]/g,'')
diff --git a/test/test.js b/test/test.js
index 9f42b35..d0d3ba9 100644
--- a/test/test.js
+++ b/test/test.js
@@ -1,6 +1,17 @@
 var assert = require('assert');
 var myanmarPhoneNumber = require('../myanmar-phonenumber.js')
 
+describe('Error throwing: ', function() {
+  it('should throw an error when empty string is passed', () => {
+    assert.throws(() => myanmarPhoneNumber.sanitizeInput('  '), Error)
+    assert.throws(() => myanmarPhoneNumber.sanitizeInput(''), Error)
+  })
+
+  it('should throw an error when "undefined" is passed', () => {
+    assert.throws(myanmarPhoneNumber.sanitizeInput, Error)
+  })
+});
+
 describe('Normalize input: ', function() {
   it('should return +959784123456 to 09784123456', function() {
     assert.equal(myanmarPhoneNumber.normalizeInput('+959784123456'), '09784123456');