diff --git a/lib/Doctrine/ORM/Mapping/Driver/XmlDriver.php b/lib/Doctrine/ORM/Mapping/Driver/XmlDriver.php
index ab8e3b780..20631d63c 100644
--- a/lib/Doctrine/ORM/Mapping/Driver/XmlDriver.php
+++ b/lib/Doctrine/ORM/Mapping/Driver/XmlDriver.php
@@ -322,8 +322,8 @@ class XmlDriver extends AbstractFileDriver
                     $mapping['orderBy'] = $orderBy;
                 }
 
-                if (isset($oneToManyElement->{'index-by'})) {
-                    $mapping['indexBy'] = (string)$oneToManyElement->{'index-by'};
+                if (isset($oneToManyElement['index-by'])) {
+                    $mapping['indexBy'] = (string)$oneToManyElement['index-by'];
                 }
 
                 $metadata->mapOneToMany($mapping);
diff --git a/tests/Doctrine/Tests/ORM/Mapping/xml/Doctrine.Tests.ORM.Mapping.User.dcm.xml b/tests/Doctrine/Tests/ORM/Mapping/xml/Doctrine.Tests.ORM.Mapping.User.dcm.xml
index 524b2494f..f116fb0fe 100644
--- a/tests/Doctrine/Tests/ORM/Mapping/xml/Doctrine.Tests.ORM.Mapping.User.dcm.xml
+++ b/tests/Doctrine/Tests/ORM/Mapping/xml/Doctrine.Tests.ORM.Mapping.User.dcm.xml
@@ -39,7 +39,7 @@
             <join-column name="address_id" referenced-column-name="id" on-delete="CASCADE" on-update="CASCADE"/>
         </one-to-one>
         
-        <one-to-many field="phonenumbers" target-entity="Phonenumber" mapped-by="user" orphan-removal="true">
+        <one-to-many field="phonenumbers" target-entity="Phonenumber" mapped-by="user" index-by="number" orphan-removal="true">
             <cascade>
                 <cascade-persist/>
             </cascade>