diff --git a/lib/PayPal/Common/PayPalModel.php b/lib/PayPal/Common/PayPalModel.php
index d90287a..8a7b177 100644
--- a/lib/PayPal/Common/PayPalModel.php
+++ b/lib/PayPal/Common/PayPalModel.php
@@ -106,7 +106,7 @@ class PayPalModel
     public function __set($key, $value)
     {
         ModelAccessorValidator::validate($this, $this->convertToCamelCase($key));
-        if (!is_array($value) && $value == null) {
+        if (!is_array($value) && $value === null) {
             $this->__unset($key);
         } else {
             $this->_propMap[$key] = $value;
diff --git a/tests/PayPal/Test/Common/PayPalModelTest.php b/tests/PayPal/Test/Common/PayPalModelTest.php
index b518cc5..d6bbef6 100644
--- a/tests/PayPal/Test/Common/PayPalModelTest.php
+++ b/tests/PayPal/Test/Common/PayPalModelTest.php
@@ -8,6 +8,7 @@ class SimpleModelTestClass extends PayPalModel
      *
      * @access public
      * @param string $field1
+     * @return self
      */
     public function setField1($field1)
     {
@@ -29,6 +30,7 @@ class SimpleModelTestClass extends PayPalModel
      *
      * @access public
      * @param string $field2
+     * @return self
      */
     public function setField2($field2)
     {
@@ -264,6 +266,29 @@ class PayPalModelTest extends PHPUnit_Framework_TestCase
         $parentCopy = new ListModelTestClass();
         $parentCopy->fromJson($parent->toJSON());
         $this->assertEquals($parent, $parentCopy);
+    }
 
+    public function EmptyNullProvider()
+    {
+        return array(
+            array(0, true),
+            array(null, false),
+            array("", true),
+            array("null", true),
+            array(-1, true),
+            array('', true)
+        );
+    }
+
+    /**
+     * @dataProvider EmptyNullProvider
+     * @param string|null $field2
+     * @param bool $matches
+     */
+    public function testEmptyNullConversion($field2, $matches)
+    {
+        $c1 = new SimpleModelTestClass();
+        $c1->setField1("a")->setField2($field2);
+        $this->assertTrue(strpos($c1->toJSON(),"field2") !== !$matches);
     }
 }