Index: /Users/darien/Documents/src/Zend/Form/Element/Multi.php
===================================================================
--- /Users/darien/Documents/src/Zend/Form/Element/Multi.php	(revision 9570)
+++ /Users/darien/Documents/src/Zend/Form/Element/Multi.php	(working copy)
@@ -241,4 +241,33 @@
             return $value;
         }
     }
+    
+    /**
+     * Extends on to the parent implementation in order to check that the value
+     * or values presented have been registered as valid options.
+     *     
+     */
+    public function isValid($value, $context = null){
+        // Do normal validation
+        $result =  parent::isValid($value,$context);
+        
+        // Add an extra check
+        $validValues = array_keys($this->getMultiOptions());
+        if(is_array($value)){
+            foreach($value as $v){
+                if(!in_array($v,$validValues)){
+                    $this->_messages[] = "One of the multiple values recieved ($v) is not a valid option.";
+                    $result = false;
+                }
+            }
+        }else{
+            if(!in_array($value,$validValues)){
+                $this->_messages[] = "Value recieved ($value) is not a valid option.";
+                $result = false;                                    
+            }
+        }
+        
+        
+        return($result);                              
+    }
 }