diff --git a/src/fastboot-headers.js b/src/fastboot-headers.js
index 1fe2549..77609c1 100644
--- a/src/fastboot-headers.js
+++ b/src/fastboot-headers.js
@@ -5,7 +5,17 @@ function FastBootHeaders(headers) {
   this.headers = {};
 
   for (var header in headers) {
-    this.headers[header] = headers[header].split(', ');
+    let value = headers[header];
+
+    // Express gives us either a string
+    // or an array of strings if there are multiple values.
+    // We want to support the Header spec
+    // so we will coerce to an array always.
+    if (typeof value === 'string') {
+      value = [value];
+    }
+
+    this.headers[header] = value;
   }
 }
 
diff --git a/test/fastboot-headers-test.js b/test/fastboot-headers-test.js
index 041ee25..014c8a5 100644
--- a/test/fastboot-headers-test.js
+++ b/test/fastboot-headers-test.js
@@ -6,23 +6,28 @@ var alchemistRequire = require('broccoli-module-alchemist/require');
 var FastBootHeaders = alchemistRequire('fastboot-headers.js');
 
 describe('FastBootHeaders', function() {
-  it('returns an array of header values from getAll, regardless of header name casing', function() {
+  it('returns an array from getAll when header value is string', function() {
     var headers = {
-      // Express concatenates repeated keys with ', '
-      // and also lowercases the keys
       'x-test-header': 'value1, value2'
     };
     headers = new FastBootHeaders(headers);
 
+    expect(headers.getAll('x-test-header')).to.deep.equal(['value1, value2']);
+  });
+
+  it('returns an array of header values from getAll, regardless of header name casing', function() {
+    var headers = {
+      'x-test-header': ['value1', 'value2']
+    };
+    headers = new FastBootHeaders(headers);
+
     expect(headers.getAll('X-Test-Header')).to.deep.equal(['value1', 'value2']);
     expect(headers.getAll('x-test-header')).to.deep.equal(['value1', 'value2']);
   });
 
   it('returns an emtpy array when a header is not present', function() {
     var headers = {
-      // Express concatenates repeated keys with ', '
-      // and also lowercases the keys
-      'x-test-header': 'value1, value2'
+      'x-test-header': ['value1', 'value2']
     };
     headers = new FastBootHeaders(headers);
 
@@ -32,9 +37,7 @@ describe('FastBootHeaders', function() {
 
   it('returns the first value when using get, regardless of case', function() {
     var headers = {
-      // Express concatenates repeated keys with ', '
-      // and also lowercases the keys
-      'x-test-header': 'value1, value2'
+      'x-test-header': ['value1', 'value2']
     };
     headers = new FastBootHeaders(headers);
 
@@ -44,9 +47,7 @@ describe('FastBootHeaders', function() {
 
   it('returns null when using get when a header is not present', function() {
     var headers = {
-      // Express concatenates repeated keys with ', '
-      // and also lowercases the keys
-      'x-test-header': 'value1, value2'
+      'x-test-header': ['value1', 'value2']
     };
     headers = new FastBootHeaders(headers);
 
@@ -56,9 +57,7 @@ describe('FastBootHeaders', function() {
 
   it('returns whether or not a header is present via has, regardless of casing', function() {
     var headers = {
-      // Express concatenates repeated keys with ', '
-      // and also lowercases the keys
-      'x-test-header': 'value1, value2'
+      'x-test-header': ['value1', 'value2']
     };
     headers = new FastBootHeaders(headers);
 
diff --git a/test/fastboot-response-test.js b/test/fastboot-response-test.js
index 304b26e..d01cd51 100644
--- a/test/fastboot-response-test.js
+++ b/test/fastboot-response-test.js
@@ -9,7 +9,7 @@ describe("FastBootResponse", function() {
   beforeEach(function () {
     var mockResponse = {
       _headers: {
-        "i-am-a": "mock header, me too",
+        "i-am-a": ["mock header", "me too"],
         "cookie": ""
       }
     };