diff --git a/lib/Doctrine/ORM/UnitOfWork.php b/lib/Doctrine/ORM/UnitOfWork.php
index c0b0dd8c3..0afabf805 100644
--- a/lib/Doctrine/ORM/UnitOfWork.php
+++ b/lib/Doctrine/ORM/UnitOfWork.php
@@ -1154,7 +1154,7 @@ class UnitOfWork implements PropertyChangedListener
 
                 $joinColumns = reset($assoc['joinColumns']);
 
-                $calc->addDependency($targetClass->name, $class->name, (int)empty($joinColumns['nullable']));
+                $calc->addDependency($targetClass->name, $class->name, (int) ! ( ! isset($joinColumns['nullable']) || $joinColumns['nullable'] === true));
 
                 // If the target class has mapped subclasses, these share the same dependency.
                 if ( ! $targetClass->subClasses) {