diff --git a/lib/mock-ajax.js b/lib/mock-ajax.js
index 2b453e2..3b628f4 100644
--- a/lib/mock-ajax.js
+++ b/lib/mock-ajax.js
@@ -233,15 +233,20 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
       },
 
       getResponseHeader: function(name) {
-        return this.responseHeaders[name];
+        var values = [];
+        for (var i = 0; i < this.responseHeaders.length; i++) {
+          if (this.responseHeaders[i].name === name) {
+            values.push(this.responseHeaders[i].value);
+          }
+        }
+        return values.join(', ');
       },
 
       getAllResponseHeaders: function() {
         var responseHeaders = [];
-        for (var i in this.responseHeaders) {
-          if (this.responseHeaders.hasOwnProperty(i)) {
-            responseHeaders.push(i + ': ' + this.responseHeaders[i]);
-          }
+        for (var i = 0; i < this.responseHeaders.length; i++) {
+          responseHeaders.push(this.responseHeaders[i].name + ': ' +
+            this.responseHeaders[i].value);
         }
         return responseHeaders.join('\r\n');
       },
@@ -256,8 +261,30 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
         this.statusText = response.statusText || "";
         this.responseText = response.responseText || "";
         this.readyState = 4;
-        this.responseHeaders = response.responseHeaders ||
-          {"Content-Type": response.contentType || "application/json" };
+        this.responseHeaders = [];
+
+        var i;
+        if (response.responseHeaders) {
+          if (response.responseHeaders instanceof Array) {
+            this.responseHeaders = response.responseHeaders;
+          } else {
+            for (i in response.responseHeaders) {
+              if (response.responseHeaders.hasOwnProperty(i)) {
+                this.responseHeaders.push({ name: i, value: response.responseHeaders[i] });
+              }
+            }
+          }
+        } else {
+          this.responseHeaders.push({ name: "Content-Type", value: response.contentType || "application/json" });
+        }
+
+        for (i = 0; i < this.responseHeaders.length; i++) {
+          if (typeof(this.responseHeaders[this.responseHeaders[i].name]) === 'undefined') {
+            this.responseHeaders[this.responseHeaders[i].name] = this.responseHeaders[i].value;
+          } else {
+            this.responseHeaders[this.responseHeaders[i].name] += ', ' + this.responseHeaders[i].value;
+          }
+        }
 
         this.onload();
         this.onreadystatechange();
diff --git a/spec/javascripts/mock-ajax-toplevel-spec.js b/spec/javascripts/mock-ajax-toplevel-spec.js
index 90d3f21..0a86cad 100644
--- a/spec/javascripts/mock-ajax-toplevel-spec.js
+++ b/spec/javascripts/mock-ajax-toplevel-spec.js
@@ -252,6 +252,83 @@ describe("Jasmine Mock Ajax (for toplevel)", function() {
       sharedAjaxResponseBehaviorForZepto_Success(sharedContext);
     });
 
+    describe("response with unique header names using an object", function () {
+      var value1, value2, value3;
+      beforeEach(function () {
+        client = new fakeGlobal.XMLHttpRequest();
+        client.onreadystatechange = onreadystatechange;
+        client.open("GET", "example.com");
+        client.send();
+
+        value1 = Math.random().toString();
+        value2 = Math.random().toString();
+        value3 = Math.random().toString();
+
+        request = mockAjax.requests.mostRecent();
+        var responseObject = {status: 200, statusText: "OK", responseText: '["foo"]', responseHeaders: {
+          'X-Header1': value1,
+          'X-Header2': value2,
+          'X-Header3': value3
+        }};
+        request.response(responseObject);
+        response = success.calls.mostRecent().args[2];
+      });
+
+      it("getResponseHeader should return the each value", function () {
+        expect(response.getResponseHeader('X-Header1')).toBe(value1);
+        expect(response.getResponseHeader('X-Header2')).toBe(value2);
+        expect(response.getResponseHeader('X-Header3')).toBe(value3);
+        expect(response.responseHeaders['X-Header1']).toBe(value1);
+        expect(response.responseHeaders['X-Header2']).toBe(value2);
+        expect(response.responseHeaders['X-Header3']).toBe(value3);
+      });
+
+      it("getAllResponseHeaders should return all values", function () {
+        expect(response.getAllResponseHeaders()).toBe([
+          "X-Header1: " + value1,
+          "X-Header2: " + value2,
+          "X-Header3: " + value3
+        ].join("\r\n"));
+      });
+    });
+
+    describe("response with multiple headers of the same name using an array of objects", function () {
+      var value1, value2, value3;
+      beforeEach(function () {
+        client = new fakeGlobal.XMLHttpRequest();
+        client.onreadystatechange = onreadystatechange;
+        client.open("GET", "example.com");
+        client.send();
+
+        value1 = Math.random().toString();
+        value2 = Math.random().toString();
+        value3 = Math.random().toString();
+
+        request = mockAjax.requests.mostRecent();
+        var responseObject = {status: 200, statusText: "OK", responseText: '["foo"]', responseHeaders: [
+          { name: 'X-Header', value: value1 },
+          { name: 'X-Header', value: value2 },
+          { name: 'X-Header', value: value3 }
+        ]};
+        request.response(responseObject);
+        response = success.calls.mostRecent().args[2];
+      });
+
+      it("getResponseHeader should return all values comma separated", function () {
+        var values = [value1, value2, value3].join(', '); // see http://www.w3.org/TR/XMLHttpRequest/#the-getresponseheader()-method
+        expect(response.getResponseHeader('X-Header')).toBe(values);
+        expect(response.responseHeaders['X-Header']).toBe(values);
+      });
+
+      it("getAllResponseHeaders should return all values", function () {
+        expect(response.getAllResponseHeaders()).toBe([
+          "X-Header: " + value1,
+          "X-Header: " + value2,
+          "X-Header: " + value3
+        ].join("\r\n"));
+      });
+    });
+
     describe("the content type defaults to application/json", function () {
       beforeEach(function() {
         client = new fakeGlobal.XMLHttpRequest();