diff --git a/src/Travis/Paypal.php b/src/Travis/Paypal.php
index 2a846ff..bbb0cc5 100644
--- a/src/Travis/Paypal.php
+++ b/src/Travis/Paypal.php
@@ -41,6 +41,7 @@ public static function __callStatic($method, $args)
             'USER' => $credentials['username'],
             'PWD' => $credentials['password'],
             'SIGNATURE' => $credentials['signature'],
+            'BUTTONSOURCE' => 'AngellEYE_SP_swt83_PHP',
             'METHOD' => static::camelcase($method),
         );