diff --git a/lib/Doctrine/ORM/Mapping/ClassMetadataFactory.php b/lib/Doctrine/ORM/Mapping/ClassMetadataFactory.php
index 36251411147..0c1936757f6 100644
--- a/lib/Doctrine/ORM/Mapping/ClassMetadataFactory.php
+++ b/lib/Doctrine/ORM/Mapping/ClassMetadataFactory.php
@@ -41,12 +41,12 @@
 use ReflectionClass;
 use ReflectionException;
 
-use function array_map;
 use function assert;
 use function class_exists;
 use function count;
 use function end;
 use function explode;
+use function in_array;
 use function is_subclass_of;
 use function strpos;
 use function strtolower;
@@ -77,18 +77,6 @@ class ClassMetadataFactory extends AbstractClassMetadataFactory
     /** @var mixed[] */
     private $embeddablesActiveNesting = [];
 
-    /**
-     * {@inheritDoc}
-     */
-    protected function loadMetadata($name)
-    {
-        $loaded = parent::loadMetadata($name);
-
-        array_map([$this, 'resolveDiscriminatorValue'], array_map([$this, 'getMetadataFor'], $loaded));
-
-        return $loaded;
-    }
-
     /**
      * @return void
      */
@@ -295,6 +283,11 @@ protected function validateRuntimeMetadata($class, $parent)
                         throw MappingException::invalidClassInDiscriminatorMap($subClass, $class->name);
                     }
                 }
+            } else {
+                assert($parent instanceof ClassMetadataInfo); // https://github.com/doctrine/orm/issues/8746
+                if ((! $class->reflClass || ! $class->reflClass->isAbstract()) && ! in_array($class->name, $parent->discriminatorMap)) {
+                    throw MappingException::mappedClassNotPartOfDiscriminatorMap($class->name, $class->rootEntityName);
+                }
             }
         } elseif ($class->isMappedSuperclass && $class->name === $class->rootEntityName && (count($class->discriminatorMap) || $class->discriminatorColumn)) {
             // second condition is necessary for mapped superclasses in the middle of an inheritance hierarchy
@@ -310,45 +303,6 @@ protected function newClassMetadataInstance($className)
         return new ClassMetadata($className, $this->em->getConfiguration()->getNamingStrategy());
     }
 
-    /**
-     * Populates the discriminator value of the given metadata (if not set) by iterating over discriminator
-     * map classes and looking for a fitting one.
-     *
-     * @throws MappingException
-     */
-    private function resolveDiscriminatorValue(ClassMetadata $metadata): void
-    {
-        if (
-            $metadata->discriminatorValue
-            || ! $metadata->discriminatorMap
-            || $metadata->isMappedSuperclass
-            || ! $metadata->reflClass
-            || $metadata->reflClass->isAbstract()
-        ) {
-            return;
-        }
-
-        // minor optimization: avoid loading related metadata when not needed
-        foreach ($metadata->discriminatorMap as $discriminatorValue => $discriminatorClass) {
-            if ($discriminatorClass === $metadata->name) {
-                $metadata->discriminatorValue = $discriminatorValue;
-
-                return;
-            }
-        }
-
-        // iterate over discriminator mappings and resolve actual referenced classes according to existing metadata
-        foreach ($metadata->discriminatorMap as $discriminatorValue => $discriminatorClass) {
-            if ($metadata->name === $this->getMetadataFor($discriminatorClass)->getName()) {
-                $metadata->discriminatorValue = $discriminatorValue;
-
-                return;
-            }
-        }
-
-        throw MappingException::mappedClassNotPartOfDiscriminatorMap($metadata->name, $metadata->rootEntityName);
-    }
-
     /**
      * Adds a default discriminator map if no one is given
      *
diff --git a/lib/Doctrine/ORM/Tools/ResolveTargetEntityListener.php b/lib/Doctrine/ORM/Tools/ResolveTargetEntityListener.php
index 63b75fc1f07..9f13b63cfb9 100644
--- a/lib/Doctrine/ORM/Tools/ResolveTargetEntityListener.php
+++ b/lib/Doctrine/ORM/Tools/ResolveTargetEntityListener.php
@@ -105,6 +105,12 @@ public function loadClassMetadata(LoadClassMetadataEventArgs $args)
                 $args->getEntityManager()->getMetadataFactory()->setMetadataFor($interface, $cm);
             }
         }
+
+        foreach ($cm->discriminatorMap as $value => $class) {
+            if (isset($this->resolveTargetEntities[$class])) {
+                $cm->addDiscriminatorMapClass($value, $this->resolveTargetEntities[$class]['targetEntity']);
+            }
+        }
     }
 
     /**
diff --git a/tests/Doctrine/Tests/ORM/Functional/Ticket/DDC3300Test.php b/tests/Doctrine/Tests/ORM/Functional/Ticket/DDC3300Test.php
index 40c96583e6f..cafb0de7257 100644
--- a/tests/Doctrine/Tests/ORM/Functional/Ticket/DDC3300Test.php
+++ b/tests/Doctrine/Tests/ORM/Functional/Ticket/DDC3300Test.php
@@ -36,8 +36,8 @@ public function testResolveTargetEntitiesChangesDiscriminatorMapValues(): void
             ]
         );
 
-        $boss     = new DDC3300HumanBoss();
-        $employee = new DDC3300HumanEmployee();
+        $boss     = new DDC3300HumanBoss('boss');
+        $employee = new DDC3300HumanEmployee('employee');
 
         $this->_em->persist($boss);
         $this->_em->persist($employee);
@@ -53,7 +53,7 @@ public function testResolveTargetEntitiesChangesDiscriminatorMapValues(): void
 /**
  * @Entity
  * @InheritanceType("SINGLE_TABLE")
- * @DdiscriminatorColumn(name="discr", type="string")
+ * @DiscriminatorColumn(name="discr", type="string")
  * @DiscriminatorMap({
  *      "boss"     = "Doctrine\Tests\ORM\Functional\Ticket\DDC3300Boss",
  *      "employee" = "Doctrine\Tests\ORM\Functional\Ticket\DDC3300Employee"
@@ -77,6 +77,16 @@ interface DDC3300Boss
 /** @Entity */
 class DDC3300HumanBoss extends DDC3300Person implements DDC3300Boss
 {
+    /**
+     * @var string
+     * @Column(type="string")
+     */
+    public $bossCol;
+
+    public function __construct($bossCol)
+    {
+        $this->bossCol = $bossCol;
+    }
 }
 
 interface DDC3300Employee
@@ -86,4 +96,14 @@ interface DDC3300Employee
 /** @Entity */
 class DDC3300HumanEmployee extends DDC3300Person implements DDC3300Employee
 {
+    /**
+     * @var string
+     * @Column(type="string")
+     */
+    public $employeeCol;
+
+    public function __construct($employeeCol)
+    {
+        $this->employeeCol = $employeeCol;
+    }
 }