diff --git a/2.0-Upgrade.md b/4.0-Upgrade.md
similarity index 94%
rename from 2.0-Upgrade.md
rename to 4.0-Upgrade.md
index 6a8ab98..3325754 100644
--- a/2.0-Upgrade.md
+++ b/4.0-Upgrade.md
@@ -1,4 +1,4 @@
-# Upgrading to chartmogul-php 2.0.0
+# Upgrading to chartmogul-php 4.0.0
 
 The package upgrade brings breaking changes to the Metrics API. All other APIs remain unaffected. Please note the following changes:
 
diff --git a/src/Http/Client.php b/src/Http/Client.php
index 55861fc..13345b6 100644
--- a/src/Http/Client.php
+++ b/src/Http/Client.php
@@ -30,7 +30,7 @@ class Client implements ClientInterface
     /**
     * @var string
     */
-    private $apiVersion = '2.0.0';
+    private $apiVersion = '4.0.0';
 
     /**
     * @var string