diff --git a/lib/PayPal/Common/PayPalModel.php b/lib/PayPal/Common/PayPalModel.php
index 65ee8dd..2cab284 100644
--- a/lib/PayPal/Common/PayPalModel.php
+++ b/lib/PayPal/Common/PayPalModel.php
@@ -175,7 +175,7 @@ class PayPalModel
         foreach ($param as $k => $v) {
             if ($v instanceof PayPalModel) {
                 $ret[$k] = $v->toArray();
-            } elseif (sizeof($v) <= 0 && is_array($v)) {
+            } elseif (is_array($v) && sizeof($v) <= 0) {
                 $ret[$k] = array();
             } elseif (is_array($v)) {
                 $ret[$k] = $this->_convertToArray($v);