diff --git a/lib/Doctrine/ORM/Persisters/Entity/JoinedSubclassPersister.php b/lib/Doctrine/ORM/Persisters/Entity/JoinedSubclassPersister.php
index de3b1e0e5f2..2679c43407d 100644
--- a/lib/Doctrine/ORM/Persisters/Entity/JoinedSubclassPersister.php
+++ b/lib/Doctrine/ORM/Persisters/Entity/JoinedSubclassPersister.php
@@ -192,14 +192,14 @@ public function executeInserts()
                 $paramIndex = 1;
                 $data       = $insertData[$tableName] ?? [];
 
-                foreach ((array) $id as $idName => $idVal) {
+                foreach ($id as $idName => $idVal) {
                     $type = $this->columnTypes[$idName] ?? Type::STRING;
 
                     $stmt->bindValue($paramIndex++, $idVal, $type);
                 }
 
                 foreach ($data as $columnName => $value) {
-                    if (! is_array($id) || ! isset($id[$columnName])) {
+                    if (! isset($id[$columnName])) {
                         $stmt->bindValue($paramIndex++, $value, $this->columnTypes[$columnName]);
                     }
                 }
diff --git a/lib/Doctrine/ORM/UnitOfWork.php b/lib/Doctrine/ORM/UnitOfWork.php
index 7aa057d2901..f500bf884b2 100644
--- a/lib/Doctrine/ORM/UnitOfWork.php
+++ b/lib/Doctrine/ORM/UnitOfWork.php
@@ -3056,12 +3056,15 @@ public function setOriginalEntityProperty($oid, $property, $value)
      *
      * @param object $entity
      *
-     * @return mixed The identifier values.
+     * @return mixed[] The identifier values.
      */
     public function getEntityIdentifier($entity)
     {
-        return $this->entityIdentifiers[spl_object_hash($entity)]
-            ?? EntityNotFoundException::noIdentifierFound(get_class($entity));
+        if (! isset($this->entityIdentifiers[spl_object_hash($entity)])) {
+            throw EntityNotFoundException::noIdentifierFound(get_class($entity));
+        }
+
+        return $this->entityIdentifiers[spl_object_hash($entity)];
     }
 
     /**
diff --git a/tests/Doctrine/Tests/ORM/UnitOfWorkTest.php b/tests/Doctrine/Tests/ORM/UnitOfWorkTest.php
index 29098887e04..0853c2960de 100644
--- a/tests/Doctrine/Tests/ORM/UnitOfWorkTest.php
+++ b/tests/Doctrine/Tests/ORM/UnitOfWorkTest.php
@@ -7,6 +7,7 @@
 use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
 use Doctrine\Common\EventManager;
+use Doctrine\ORM\EntityNotFoundException;
 use Doctrine\ORM\Events;
 use Doctrine\ORM\Mapping\ClassMetadata;
 use Doctrine\ORM\OptimisticLockException;
@@ -815,6 +816,12 @@ public function testCommitThrowOptimisticLockExceptionWhenConnectionCommitReturn
         $this->expectException(OptimisticLockException::class);
         $this->_unitOfWork->commit();
     }
+
+    public function testItThrowsWhenLookingUpIdentifierForUnknownEntity(): void
+    {
+        $this->expectException(EntityNotFoundException::class);
+        $this->_unitOfWork->getEntityIdentifier(new stdClass());
+    }
 }
 
 /**