diff --git a/lib/Doctrine/ORM/Mapping/Driver/YamlDriver.php b/lib/Doctrine/ORM/Mapping/Driver/YamlDriver.php
index c4fb45ece..fa5201393 100644
--- a/lib/Doctrine/ORM/Mapping/Driver/YamlDriver.php
+++ b/lib/Doctrine/ORM/Mapping/Driver/YamlDriver.php
@@ -806,10 +806,6 @@ class YamlDriver extends FileDriver
      */
     protected function loadMappingFile($file)
     {
-        if (defined(Yaml::class . '::PARSE_KEYS_AS_STRINGS')) {
-            return Yaml::parse(file_get_contents($file), Yaml::PARSE_KEYS_AS_STRINGS);
-        }
-
         return Yaml::parse(file_get_contents($file));
     }
 }