diff --git a/library/think/Model.php b/library/think/Model.php
index 77ef71fa..95a346e1 100644
--- a/library/think/Model.php
+++ b/library/think/Model.php
@@ -76,7 +76,7 @@ class Model
 
         if (!empty($config['prefix'])) {
             $this->tablePrefix = $config['prefix'];
-        } elseif ('' === $config['prefix']) {
+        } elseif (isset($config['prefix']) && '' === $config['prefix']) {
             $this->tablePrefix = '';
         } elseif (is_null($this->tablePrefix)) {
             $this->tablePrefix = Config::get('database.prefix');