diff --git a/lib/PayPal/Core/PayPalConstants.php b/lib/PayPal/Core/PayPalConstants.php
index eb63ed41..2bd8c2d7 100644
--- a/lib/PayPal/Core/PayPalConstants.php
+++ b/lib/PayPal/Core/PayPalConstants.php
@@ -12,7 +12,7 @@ class PayPalConstants
 {
 
     const SDK_NAME = 'PayPal-PHP-SDK';
-    const SDK_VERSION = '1.5.1';
+    const SDK_VERSION = '1.6.1';
 
     /**
      * Approval URL for Payment
diff --git a/release_notes.md b/release_notes.md
index fdc42bd6..47bcc784 100644
--- a/release_notes.md
+++ b/release_notes.md
@@ -1,5 +1,17 @@
 PayPal PHP SDK release notes
 ============================
+
+v1.6.1
+----
+* User Agent Changes
+* SDK Version Fix
+
+v1.6.0
+----
+* Updated Payments API to latest version
+* Removed ModelAccessValidator
+* Minor Bug Fixes #399
+
 v1.5.1
 ----
 * Fixed a bug #343 in Future Payment