diff --git a/lib/Doctrine/ORM/Mapping/Driver/YamlDriver.php b/lib/Doctrine/ORM/Mapping/Driver/YamlDriver.php
index 8793c070b..5161ed0f0 100644
--- a/lib/Doctrine/ORM/Mapping/Driver/YamlDriver.php
+++ b/lib/Doctrine/ORM/Mapping/Driver/YamlDriver.php
@@ -800,6 +800,10 @@ 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));
     }
 }
diff --git a/tests/Doctrine/Tests/ORM/Mapping/yaml/Doctrine.Tests.Models.CMS.CmsUser.dcm.yml b/tests/Doctrine/Tests/ORM/Mapping/yaml/Doctrine.Tests.Models.CMS.CmsUser.dcm.yml
index 3a03dd6c3..329e3d061 100644
--- a/tests/Doctrine/Tests/ORM/Mapping/yaml/Doctrine.Tests.Models.CMS.CmsUser.dcm.yml
+++ b/tests/Doctrine/Tests/ORM/Mapping/yaml/Doctrine.Tests.Models.CMS.CmsUser.dcm.yml
@@ -135,7 +135,6 @@ Doctrine\Tests\Models\CMS\CmsUser:
         name: address_id
         referencedColumnName: id
       cascade: [ persist ]
-  oneToOne:
     email:
       targetEntity: CmsEmail
       orphanRemoval: true
@@ -155,4 +154,4 @@ Doctrine\Tests\Models\CMS\CmsUser:
         inverseJoinColumns:
           group_id:
             referencedColumnName: id
-      cascade: [ persist , detach, merge]
\ No newline at end of file
+      cascade: [ persist , detach, merge]
diff --git a/tests/Doctrine/Tests/ORM/Mapping/yaml/Doctrine.Tests.Models.Company.CompanyPerson.dcm.yml b/tests/Doctrine/Tests/ORM/Mapping/yaml/Doctrine.Tests.Models.Company.CompanyPerson.dcm.yml
index 26846c5de..28eec43e3 100644
--- a/tests/Doctrine/Tests/ORM/Mapping/yaml/Doctrine.Tests.Models.Company.CompanyPerson.dcm.yml
+++ b/tests/Doctrine/Tests/ORM/Mapping/yaml/Doctrine.Tests.Models.Company.CompanyPerson.dcm.yml
@@ -52,7 +52,6 @@ Doctrine\Tests\Models\Company\CompanyPerson:
         name: address_id
         referencedColumnName: id
       cascade: [ persist ]
-  oneToOne:
     email:
       targetEntity: CmsEmail
       orphanRemoval: true
@@ -72,4 +71,4 @@ Doctrine\Tests\Models\Company\CompanyPerson:
         inverseJoinColumns:
           group_id:
             referencedColumnName: id
-      cascade: [ persist , detach, merge]
\ No newline at end of file
+      cascade: [ persist , detach, merge]