diff --git a/CHANGES.md b/CHANGES.md
index 35bd957..0e0c55a 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,5 +1,9 @@
 - warns instead of throwing when validating actions
 
+## v3.3.1
+- adding API versioning
+
+
 ## v3.3.0
 
 - callbacks are not called asynchronously by default, choice is left to the developer (use process.nextTick in your callback to emulate the previous behavior)
diff --git a/lib/wit.js b/lib/wit.js
index cda60c9..6a67c49 100644
--- a/lib/wit.js
+++ b/lib/wit.js
@@ -8,6 +8,7 @@ const logLevels = require('./logger').logLevels;
 
 const DEFAULT_MAX_STEPS = 5;
 const CALLBACK_TIMEOUT_MS = 10000;
+const API_VERSION = '20160516';
 
 let l = new Logger(logLevels.LOG);
 
@@ -125,7 +126,7 @@ const Wit = function(token, actions, logger) {
       cb = context;
       context = undefined;
     }
-    let qs = 'q=' + encodeURIComponent(message);
+    let qs = 'v='+ API_VERSION +'&q=' + encodeURIComponent(message);
     if (context) {
       qs += '&context=' + encodeURIComponent(JSON.stringify(context));
     }
@@ -142,7 +143,7 @@ const Wit = function(token, actions, logger) {
 
   this.converse = (sessionId, message, context, cb) => {
     const handler = makeWitResponseHandler('converse', l, cb);
-    let qs = 'session_id=' + sessionId;
+    let qs = 'v='+ API_VERSION + '&session_id=' + sessionId;
     if (message) {
       qs += '&q=' + encodeURIComponent(message);
     }
diff --git a/package.json b/package.json
index e623b2b..905f2bb 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "node-wit",
-  "version": "3.3.0",
+  "version": "3.3.1",
   "description": "Wit.ai Node.js SDK",
   "keywords": [
     "wit",