diff --git a/lib/Doctrine/ORM/Internal/Hydration/AbstractHydrator.php b/lib/Doctrine/ORM/Internal/Hydration/AbstractHydrator.php
index b38a212c9..5fe4fa1e5 100644
--- a/lib/Doctrine/ORM/Internal/Hydration/AbstractHydrator.php
+++ b/lib/Doctrine/ORM/Internal/Hydration/AbstractHydrator.php
@@ -24,6 +24,8 @@ use Doctrine\ORM\EntityManagerInterface;
 use Doctrine\ORM\Events;
 use Doctrine\ORM\Mapping\ClassMetadata;
 use PDO;
+use function array_map;
+use function in_array;
 
 /**
  * Base class for all hydrators. A hydrator is a class that provides some form
@@ -296,11 +298,8 @@ abstract class AbstractHydrator
 
                     // If there are field name collisions in the child class, then we need
                     // to only hydrate if we are looking at the correct discriminator value
-                    if(
-                        isset($cacheKeyInfo['discriminatorColumn']) && 
-                        isset($data[$cacheKeyInfo['discriminatorColumn']]) &&
-                        // Note: loose comparison required. See https://github.com/doctrine/doctrine2/pull/6304#issuecomment-323294442
-                        $data[$cacheKeyInfo['discriminatorColumn']] != $cacheKeyInfo['discriminatorValue']
+                    if (isset($cacheKeyInfo['discriminatorColumn'], $data[$cacheKeyInfo['discriminatorColumn']])
+                        && ! in_array((string) $data[$cacheKeyInfo['discriminatorColumn']], $cacheKeyInfo['discriminatorValues'], true)
                     ) {
                         break;
                     }
@@ -401,7 +400,8 @@ abstract class AbstractHydrator
                         $columnInfo,
                         [
                             'discriminatorColumn' => $this->_rsm->discriminatorColumns[$ownerMap],
-                            'discriminatorValue'  => $classMetadata->discriminatorValue
+                            'discriminatorValue'  => $classMetadata->discriminatorValue,
+                            'discriminatorValues' => $this->getDiscriminatorValues($classMetadata),
                         ]
                     );
                 }
@@ -454,6 +454,23 @@ abstract class AbstractHydrator
         return null;
     }
 
+    /**
+     * @return string[]
+     */
+    private function getDiscriminatorValues(ClassMetadata $classMetadata) : array
+    {
+        $values = array_map(
+            function (string $subClass) : string {
+                return (string) $this->getClassMetadata($subClass)->discriminatorValue;
+            },
+            $classMetadata->subClasses
+        );
+
+        $values[] = (string) $classMetadata->discriminatorValue;
+
+        return $values;
+    }
+
     /**
      * Retrieve ClassMetadata associated to entity class name.
      *
diff --git a/tests/Doctrine/Tests/ORM/Functional/Ticket/GH6937Test.php b/tests/Doctrine/Tests/ORM/Functional/Ticket/GH6937Test.php
new file mode 100644
index 000000000..756111b98
--- /dev/null
+++ b/tests/Doctrine/Tests/ORM/Functional/Ticket/GH6937Test.php
@@ -0,0 +1,119 @@
+<?php
+
+namespace Doctrine\Tests\ORM\Functional\Ticket;
+
+use Doctrine\ORM\AbstractQuery;
+use Doctrine\Tests\OrmFunctionalTestCase;
+
+/**
+ * @group 6937
+ */
+final class GH6937Test extends OrmFunctionalTestCase
+{
+    /**
+     * {@inheritDoc}
+     */
+    protected function setUp() : void
+    {
+        parent::setUp();
+
+        $this->setUpEntitySchema([GH6937Person::class, GH6937Employee::class, GH6937Manager::class]);
+    }
+
+    public function testPhoneNumberIsPopulatedWithFind() : void
+    {
+        $manager              = new GH6937Manager();
+        $manager->name        = 'Kevin';
+        $manager->phoneNumber = '555-5555';
+        $manager->department  = 'Accounting';
+
+        $this->_em->persist($manager);
+        $this->_em->flush();
+        $this->_em->clear();
+
+        $persistedManager = $this->_em->find(GH6937Person::class, $manager->id);
+
+        self::assertSame('Kevin', $persistedManager->name);
+        self::assertSame('555-5555', $persistedManager->phoneNumber);
+        self::assertSame('Accounting', $persistedManager->department);
+    }
+
+    public function testPhoneNumberIsPopulatedWithQueryBuilderUsingSimpleObjectHydrator() : void
+    {
+        $manager              = new GH6937Manager();
+        $manager->name        = 'Kevin';
+        $manager->phoneNumber = '555-5555';
+        $manager->department  = 'Accounting';
+
+        $this->_em->persist($manager);
+        $this->_em->flush();
+        $this->_em->clear();
+
+        $persistedManager = $this->_em->getRepository(GH6937Person::class)
+                                      ->createQueryBuilder('e')
+                                      ->where('e.id = :id')
+                                      ->setParameter('id', $manager->id)
+                                      ->getQuery()
+                                      ->getOneOrNullResult(AbstractQuery::HYDRATE_SIMPLEOBJECT);
+
+        self::assertSame('Kevin', $persistedManager->name);
+        self::assertSame('555-5555', $persistedManager->phoneNumber);
+        self::assertSame('Accounting', $persistedManager->department);
+    }
+
+    public function testPhoneNumberIsPopulatedWithQueryBuilder() : void
+    {
+        $manager              = new GH6937Manager();
+        $manager->name        = 'Kevin';
+        $manager->phoneNumber = '555-5555';
+        $manager->department  = 'Accounting';
+
+        $this->_em->persist($manager);
+        $this->_em->flush();
+        $this->_em->clear();
+
+        $persistedManager = $this->_em->getRepository(GH6937Person::class)
+                                      ->createQueryBuilder('e')
+                                      ->where('e.id = :id')
+                                      ->setParameter('id', $manager->id)
+                                      ->getQuery()
+                                      ->getOneOrNullResult();
+
+        self::assertSame('Kevin', $persistedManager->name);
+        self::assertSame('555-5555', $persistedManager->phoneNumber);
+        self::assertSame('Accounting', $persistedManager->department);
+    }
+}
+
+/**
+ * @Entity
+ * @InheritanceType("JOINED")
+ * @DiscriminatorColumn(name="discr", type="string")
+ * @DiscriminatorMap({"employee"=GH6937Employee::class, "manager"=GH6937Manager::class})
+ */
+abstract class GH6937Person
+{
+    /** @Id @Column(type="integer") @GeneratedValue */
+    public $id;
+
+    /** @Column(type="string") */
+    public $name;
+}
+
+/**
+ * @Entity
+ */
+abstract class GH6937Employee extends GH6937Person
+{
+    /** @Column(type="string") */
+    public $phoneNumber;
+}
+
+/**
+ * @Entity
+ */
+class GH6937Manager extends GH6937Employee
+{
+    /** @Column(type="string") */
+    public $department;
+}