diff --git a/lib/Doctrine/ORM/Tools/SchemaTool.php b/lib/Doctrine/ORM/Tools/SchemaTool.php
index d9197f502..3edb16425 100644
--- a/lib/Doctrine/ORM/Tools/SchemaTool.php
+++ b/lib/Doctrine/ORM/Tools/SchemaTool.php
@@ -248,7 +248,7 @@ class SchemaTool
         $column['type'] = Type::getType($mapping['type']);
         $column['length'] = isset($mapping['length']) ? $mapping['length'] : null;
         $column['notnull'] = isset($mapping['nullable']) ? ! $mapping['nullable'] : false;
-        $column['unique'] = isset($mapping['unique']) ? ! $mapping['unique'] : false;
+        $column['unique'] = isset($mapping['unique']) ? $mapping['unique'] : false;
 
         if (isset($mapping['precision'])) {
             $column['precision'] = $mapping['precision'];