diff --git a/index.js b/index.js
index 35ea5a84..a16713a9 100644
--- a/index.js
+++ b/index.js
@@ -193,7 +193,7 @@ function session(options){
       var ret;
       var sync = true;
 
-      if (chunk === undefined) {
+      if (chunk === undefined || chunk === null) {
         chunk = '';
       }
 
diff --git a/test/session.js b/test/session.js
index 0481d78c..8b0e510a 100644
--- a/test/session.js
+++ b/test/session.js
@@ -184,6 +184,34 @@ describe('session()', function(){
     .expect(200, 'Hello, world!', done);
   })
 
+  it('should handle HEAD requests which respond with undefined bodies', function (done) {
+    var app = express()
+
+    app.use(createSession())
+    app.use(function (req, res) {
+      res.setHeader('Content-Length', 1)
+      res.end(undefined, 'utf8')
+    })
+
+    request(app)
+    .head('/')
+    .expect(200, '', done)
+  })
+
+  it('should handle HEAD requests which respond with null bodies', function (done) {
+    var app = express()
+
+    app.use(createSession())
+    app.use(function (req, res) {
+      res.setHeader('Content-Length', 1)
+      res.end(null, 'utf8')
+    })
+
+    request(app)
+    .head('/')
+    .expect(200, '', done)
+  })
+
   describe('when response ended', function () {
     it('should have saved session', function (done) {
       var saved = false