diff --git a/library/Zend/Validate/File/Upload.php b/library/Zend/Validate/File/Upload.php
index fde3414c93..1e051b8823 100644
--- a/library/Zend/Validate/File/Upload.php
+++ b/library/Zend/Validate/File/Upload.php
@@ -161,7 +161,9 @@ public function setFiles($files = array())
      */
     public function isValid($value, $file = null)
     {
-        $this->_messages = null;
+        $this->_messages = array();
+        $files = array();
+
         if (array_key_exists($value, $this->_files)) {
             $files[$value] = $this->_files[$value];
         } else {