Index: library/Zend/Form.php
===================================================================
--- library/Zend/Form.php	(revision 23576)
+++ library/Zend/Form.php	(working copy)
@@ -1013,6 +1013,7 @@
      * @param  string|Zend_Form_Element $element
      * @param  string $name
      * @param  array|Zend_Config $options
+     * @throws Zend_Form_Exception on invalid element
      * @return Zend_Form
      */
     public function addElement($element, $name = null, $options = null)
@@ -1050,6 +1051,9 @@
 
             $this->_elements[$name] = $element;
             $this->_elements[$name]->addPrefixPaths($prefixPaths);
+        } else {
+            require_once 'Zend/Form/Exception.php';
+            throw new Zend_Form_Exception('Element must be specified by string or Zend_Form_Element instance');
         }
 
         $this->_order[$name] = $this->_elements[$name]->getOrder();
Index: tests/Zend/Form/FormTest.php
===================================================================
--- tests/Zend/Form/FormTest.php	(revision 23576)
+++ tests/Zend/Form/FormTest.php	(working copy)
@@ -4415,6 +4415,16 @@
         }
         $this->assertNotEquals($result,'');
     }
+    
+    /**
+     * @group ZF-10865
+     * @expectedException Zend_Form_Exception
+     */
+    public function testExceptionThrownWhenAddElementsIsGivenNullValue()
+    {
+        $form = new Zend_Form();
+        $form->addElement(NULL);
+    }
 }
 
 class Zend_Form_FormTest_DisplayGroup extends Zend_Form_DisplayGroup