3 files changed, 27 insertions, 14 deletions
diff --git a/README.md b/README.md
index 1df72f8..310ce8e 100644
--- a/README.md
+++ b/README.md
@@ -208,8 +208,8 @@ You can add custom headers. This will ADD rather than SET headers.
 ```javascript
 var email     = new sendgrid.Email(); 
 email.setHeaders({full: 'hearts'});   // headers = {full: 'hearts'}
-email.addHeader({spin: 'attack'});   // headers = {full: 'hearts', spin: 'attack'}
-email.addHeader({mask: 'salesman'}); // headers = {full: 'hearts', spin: 'attack', mask: 'salesman'}
+email.addHeader('spin', 'attack');   // headers = {full: 'hearts', spin: 'attack'}
+email.addHeader('mask', 'salesman'); // headers = {full: 'hearts', spin: 'attack', mask: 'salesman'}
 sendgrid.send(email, function(err, json) { });
 ```
 
diff --git a/lib/email.js b/lib/email.js
index c369530..902dd46 100644
--- a/lib/email.js
+++ b/lib/email.js
@@ -52,9 +52,17 @@ function Email(params) {
   }
 }
 
-Email.prototype.addHeader = function(object_literal) {
-  if (_.isObject(object_literal)) {
-    _.extend(this.headers, object_literal);
+Email.prototype.addHeader = function(object_literal_or_key, value) {
+  if (typeof value === "undefined" || value === null) { 
+    value = ""; 
+  }
+
+  if (_.isObject(object_literal_or_key)) {
+    _.extend(this.headers, object_literal_or_key);
+  } else {
+    var object_to_add = {}
+    object_to_add[object_literal_or_key] = value;
+    _.extend(this.headers, object_to_add);
   }
 };
 
diff --git a/test/lib/email.test.js b/test/lib/email.test.js
index 8a659c4..9ecf3c1 100644
--- a/test/lib/email.test.js
+++ b/test/lib/email.test.js
@@ -221,7 +221,20 @@ describe('Email', function () {
       expect(mail.headers).to.eql(custom_headers);
     });
 
-    it('should allow setting custom headers one at a time with addHeader', function() {
+    it('should allow setting custom headers with key, value approach', function() {
+      mail.addHeader('fox', 'hound');
+      expect(mail.headers.fox).to.eql('hound');
+    });
+
+    it('should overwrite headers when calling addHeader with the same value', function() {
+      mail.addHeader(custom_headers);
+      expect(mail.headers).to.eql(custom_headers);
+      mail.addHeader('cow', 'in my mind');
+      expect(mail.headers).not.to.eql(custom_headers);
+      expect(mail.headers.cow).to.eql('in my mind');
+    });
+
+    it('should allow setting custom headers one at a time with addHeader as a hash (temporary. deprecate this ability for key, value approach instead)', function() {
       for(var key in custom_headers) {
         var args = {};
         args[key] = custom_headers[key];
@@ -233,14 +246,6 @@ describe('Email', function () {
       expect(mail.headers.fox).to.eql('hound');
     });
 
-    it('should overwrite headers when calling addHeader with the same value', function() {
-      mail.addHeader(custom_headers);
-      expect(mail.headers).to.eql(custom_headers);
-      mail.addHeader({cow: 'in my mind'});
-      expect(mail.headers).not.to.eql(custom_headers);
-      expect(mail.headers.cow).to.eql('in my mind');
-    });
-
   });
 
   describe('file handling the constructor', function() {