diff --git a/index.js b/index.js
index 2241d974..caf32a3d 100644
--- a/index.js
+++ b/index.js
@@ -18,7 +18,7 @@ var crc = require('crc').crc32;
 var debug = require('debug')('express-session');
 var deprecate = require('depd')('express-session');
 var parseUrl = require('parseurl');
-var uid = require('uid-safe').sync
+var uid = require('uid-safe')
   , onHeaders = require('on-headers')
   , signature = require('cookie-signature')
 
@@ -89,8 +89,11 @@ function session(options) {
   // get the cookie options
   var cookieOptions = opts.cookie || {}
 
+  // toggle asynchronous session generation
+  var isAsync = !!opts.async
+
   // get the session id generate function
-  var generateId = opts.genid || generateSessionId
+  var generateId = opts.genid || (isAsync ? generateSessionId : generateSessionIdSync)
 
   // get the session cookie name
   var name = opts.name || opts.key || 'connect.sid'
@@ -154,13 +157,27 @@ function session(options) {
   }
 
   // generates the new session
-  store.generate = function(req){
-    req.sessionID = generateId(req);
-    req.session = new Session(req);
-    req.session.cookie = new Cookie(cookieOptions);
+  store.generate = function(req, callback) {
+    if (isAsync) {
+      generateId(req, initializeSession);
+    } else {
+      initializeSession(null, generateId(req));
+    }
+
+    // Initializes session and cookie
+    function initializeSession(err, sessionID) {
+      if(err) throw err;
+
+      req.sessionID = sessionID;
+
+      req.session = new Session(req);
+      req.session.cookie = new Cookie(cookieOptions);
+
+      if (cookieOptions.secure === 'auto') {
+        req.session.cookie.secure = issecure(req, trustProxy);
+      }
 
-    if (cookieOptions.secure === 'auto') {
-      req.session.cookie.secure = issecure(req, trustProxy);
+      callback(req);
     }
   };
 
@@ -207,7 +224,6 @@ function session(options) {
     var originalHash;
     var originalId;
     var savedHash;
-    var touched = false
 
     // expose store
     req.sessionStore = store;
@@ -232,11 +248,8 @@ function session(options) {
         return;
       }
 
-      if (!touched) {
-        // touch session
-        req.session.touch()
-        touched = true
-      }
+      // touch session
+      req.session.touch();
 
       // set cookie
       setcookie(res, name, req.sessionID, secrets[0], req.session.cookie.data);
@@ -320,12 +333,6 @@ function session(options) {
         return _end.call(res, chunk, encoding);
       }
 
-      if (!touched) {
-        // touch session
-        req.session.touch()
-        touched = true
-      }
-
       if (shouldSave(req)) {
         req.session.save(function onsave(err) {
           if (err) {
@@ -355,11 +362,13 @@ function session(options) {
     };
 
     // generate the session
-    function generate() {
-      store.generate(req);
-      originalId = req.sessionID;
-      originalHash = hash(req.session);
-      wrapmethods(req.session);
+    function generate(callback) {
+      store.generate(req, function(req) {
+        originalId = req.sessionID;
+        originalHash = hash(req.session);
+        wrapmethods(req.session);
+        callback && callback();
+      });
     }
 
     // wrap session methods
@@ -434,8 +443,9 @@ function session(options) {
     // generate a session if the browser doesn't send a sessionID
     if (!req.sessionID) {
       debug('no SID sent, generating session');
-      generate();
-      next();
+      generate(function(){
+        next();
+      });
       return;
     }
 
@@ -451,11 +461,15 @@ function session(options) {
           return;
         }
 
-        generate();
+        generate(function(){
+          next();
+        });
       // no session
       } else if (!sess) {
         debug('no session found');
-        generate();
+        generate(function(){
+          next();
+        });
       // populate req.session
       } else {
         debug('session found');
@@ -468,9 +482,9 @@ function session(options) {
         }
 
         wrapmethods(req.session);
-      }
 
-      next();
+        next();
+      }
     });
   };
 };
@@ -482,8 +496,19 @@ function session(options) {
  * @private
  */
 
-function generateSessionId(sess) {
-  return uid(24);
+function generateSessionId(sess, callback) {
+  return uid(24, callback);
+}
+
+/**
+ * Generate a session ID for a new session synchronously.
+ *
+ * @return {String}
+ * @private
+ */
+
+function generateSessionIdSync(sess, callback) {
+  return uid.sync(24);
 }
 
 /**
diff --git a/test/session.js b/test/session.js
index 9eb3d38e..eee9aaf5 100644
--- a/test/session.js
+++ b/test/session.js
@@ -72,6 +72,23 @@ describe('session()', function(){
     })
   })
 
+  it('should generate req.sessionID asynchronously', function (done) {
+    var sessionID = Math.random().toString(16)
+    var server = createServer({ async: true, genid: function(req, callback) { setTimeout(callback.bind(null, null, sessionID), 10) } }, function (req, res) {
+      res.end(req.sessionID)
+    });
+
+    request(server)
+    .get('/')
+    .expect(shouldSetCookie('connect.sid'))
+    .expect(200, sessionID, function (err, res) {
+      if (err) return done(err)
+      shouldSetCookie(res)
+      assert(res.headers['set-cookie'][0].indexOf(sessionID) > -1)
+      done()
+    })
+  })
+
   it('should load session from cookie sid', function (done) {
     var count = 0
     var server = createServer(null, function (req, res) {
@@ -396,43 +413,6 @@ describe('session()', function(){
         done()
       })
     })
-
-    it('should have saved session with updated cookie expiration', function (done) {
-      var store = new session.MemoryStore()
-      var server = createServer({ cookie: { maxAge: min }, store: store }, function (req, res) {
-        req.session.user = 'bob'
-        res.end(req.session.id)
-      })
-
-      request(server)
-      .get('/')
-      .expect(shouldSetCookie('connect.sid'))
-      .expect(200, function (err, res) {
-        if (err) return done(err)
-        var id = res.text
-        store.get(id, function (err, sess) {
-          if (err) return done(err)
-          assert.ok(sess, 'session saved to store')
-          var exp = new Date(sess.cookie.expires)
-          assert.equal(exp.toUTCString(), expires(res))
-          setTimeout(function () {
-            request(server)
-            .get('/')
-            .set('Cookie', cookie(res))
-            .expect(200, function (err, res) {
-              if (err) return done(err)
-              store.get(id, function (err, sess) {
-                if (err) return done(err)
-                assert.equal(res.text, id)
-                assert.ok(sess, 'session still in store')
-                assert.notEqual(new Date(sess.cookie.expires).toUTCString(), exp.toUTCString(), 'session cookie expiration updated')
-                done()
-              })
-            })
-          }, (1000 - (Date.now() % 1000) + 200))
-        })
-      })
-    })
   })
 
   describe('when sid not in store', function () {