Index: library/Zend/Form.php
===================================================================
--- library/Zend/Form.php	(revision 23428)
+++ library/Zend/Form.php	(revision )
@@ -1786,7 +1786,7 @@
         $group = array();
         foreach ($elements as $element) {
             if($element instanceof Zend_Form_Element) {
-                $element = $element->getId();
+                $element = $element->getName();
             }
 
             if (isset($this->_elements[$element])) {
Index: tests/Zend/Form/FormTest.php
===================================================================
--- tests/Zend/Form/FormTest.php	(revision 23427)
+++ tests/Zend/Form/FormTest.php	(revision )
@@ -4392,10 +4392,14 @@
     public function testAddElementToDisplayGroupByElementInstance()
     {
         $element = new Zend_Form_Element_Text('foo');
+        $elementTwo = new Zend_Form_Element_Text('baz-----');
 
-        $this->form->addElement($element);
-        $this->form->addDisplayGroup(array($element), 'bar');
-        $this->assertNotNull($this->form->getDisplayGroup('bar')->getElement('foo'));
+        $this->form->addElements(array($element, $elementTwo));
+        $this->form->addDisplayGroup(array($element, $elementTwo), 'bar');
+
+        $displayGroup = $this->form->getDisplayGroup('bar');
+        $this->assertNotNull($displayGroup->getElement('foo'));
+        $this->assertNotNull($displayGroup->getElement('baz'));
     }
 
     /**