diff --git a/README.md b/README.md
index b88ed824..ebc6fbce 100644
--- a/README.md
+++ b/README.md
@@ -462,6 +462,24 @@ called as `callback(error)` once the session has been set in the store.
 
 ### store.touch(sid, session, callback)
 
+##### sessionid
+
+Function to manually set the sessionID. This is most helpful for environments where
+cookies are not possible. When the expression returns no value, the regular sessionID
+will be used or generated.
+
+**NOTE** be careful with unsecured connections. When you don't use SSL, a man in the
+middle could intercept a sessionID and pick up a session from there.
+
+```js
+app.use(session({
+  sessionid: function(req) {
+    return req.query.sessionID;
+  },
+  secret: 'keyboard cat'
+}))
+```
+
 **Recommended**
 
 This recommended method is used to "touch" a given session given a
diff --git a/index.js b/index.js
index 5794118f..10a30381 100644
--- a/index.js
+++ b/index.js
@@ -75,6 +75,7 @@ var defer = typeof setImmediate === 'function'
  * @param {Boolean} [options.proxy]
  * @param {Boolean} [options.resave] Resave unmodified sessions back to the store
  * @param {Boolean} [options.rolling] Enable/disable rolling session expiration
+ * @param {Function} [options.sessionid] Manually set session ID
  * @param {Boolean} [options.saveUninitialized] Save uninitialized sessions to the store
  * @param {String|Array} [options.secret] Secret for signing session ID
  * @param {Object} [options.store=MemoryStore] Session store
@@ -97,7 +98,9 @@ function session(options) {
 
   // get the session store
   var store = opts.store || new MemoryStore()
-
+ 
+  var getManualSessionId = options.sessionid || function(req) {};
+  
   // get the trust proxy setting
   var trustProxy = opts.proxy
 
@@ -155,7 +158,7 @@ function session(options) {
 
   // generates the new session
   store.generate = function(req){
-    req.sessionID = generateId(req);
+    req.sessionID = getManualSessionId(req) ? getManualSessionId(req) : generateId(req);
     req.session = new Session(req);
     req.session.cookie = new Cookie(cookieOptions);
 
@@ -212,7 +215,7 @@ function session(options) {
     req.sessionStore = store;
 
     // get the session ID from the cookie
-    var cookieId = req.sessionID = getcookie(req, name, secrets);
+    var cookieId = req.sessionID = getManualSessionId(req) ? getManualSessionId(req) : getcookie(req, name, secrets)
 
     // set-cookie
     onHeaders(res, function(){