diff --git a/lib/mock-ajax.js b/lib/mock-ajax.js
index ae66b0d..07020aa 100644
--- a/lib/mock-ajax.js
+++ b/lib/mock-ajax.js
@@ -172,6 +172,15 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
       this.requestHeaders = {};
     }
 
+    function findHeader(name, headers) {
+      name = name.toLowerCase();
+      for (var header in headers) {
+        if (header.toLowerCase() === name) {
+          return headers[header];
+        }
+      }
+    }
+
     var iePropertiesThatCannotBeCopied = ['responseBody', 'responseText', 'responseXML', 'status', 'statusText', 'responseTimeout'];
     extend(FakeXMLHttpRequest.prototype, new window.XMLHttpRequest(), iePropertiesThatCannotBeCopied);
     extend(FakeXMLHttpRequest.prototype, {
@@ -221,11 +230,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
       },
 
       contentType: function() {
-        for (var header in this.requestHeaders) {
-          if (header.toLowerCase() === 'content-type') {
-            return this.requestHeaders[header];
-          }
-        }
+        return findHeader('content-type', this.requestHeaders);
       },
 
       data: function() {
@@ -237,7 +242,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
       },
 
       getResponseHeader: function(name) {
-        return this.responseHeaders[name];
+        return findHeader(name, this.responseHeaders);
       },
 
       getAllResponseHeaders: function() {
diff --git a/spec/javascripts/fake-xml-http-request-spec.js b/spec/javascripts/fake-xml-http-request-spec.js
index 8f863a3..9f07891 100644
--- a/spec/javascripts/fake-xml-http-request-spec.js
+++ b/spec/javascripts/fake-xml-http-request-spec.js
@@ -219,12 +219,26 @@ describe("FakeXMLHttpRequest", function() {
       expect(xhr.contentType()).toEqual('something');
     });
 
-    it("gets the content-type even when the casing is not to spec", function() {
+    it("gets the content-type case-insensitively", function() {
       xhr.setRequestHeader('content-Type', 'some other thing');
       expect(xhr.contentType()).toEqual('some other thing');
     });
   });
 
+  describe("getResponseHeader", function() {
+    it("gets a response header case-insensitively", function() {
+      xhr.send();
+      xhr.response({
+        status: 200,
+        responseHeaders: {
+          'X-Foo': 'Bar'
+        }
+      });
+
+      expect(xhr.getResponseHeader('x-foo')).toBe('Bar');
+    });
+  });
+
   describe("when a fake XMLHttpRequest is created", function() {
     it("inherits the properties of the real XMLHttpRequest object", function() {
       expect(xhr.someOtherProperty).toBe('someValue');