diff --git a/lib/Doctrine/ORM/Tools/SchemaTool.php b/lib/Doctrine/ORM/Tools/SchemaTool.php
index db9438c9f..7b088f578 100644
--- a/lib/Doctrine/ORM/Tools/SchemaTool.php
+++ b/lib/Doctrine/ORM/Tools/SchemaTool.php
@@ -433,7 +433,7 @@ class SchemaTool
             $knownOptions = array('comment', 'unsigned', 'fixed', 'default');
 
             foreach ($knownOptions as $knownOption) {
-                if ( isset($mapping['options'][$knownOption])) {
+                if (array_key_exists($knownOption, $mapping['options'])) {
                     $options[$knownOption] = $mapping['options'][$knownOption];
 
                     unset($mapping['options'][$knownOption]);