diff --git a/src/UnitOfWork.php b/src/UnitOfWork.php
index b07bf8aa51..e6fb891798 100644
--- a/src/UnitOfWork.php
+++ b/src/UnitOfWork.php
@@ -67,6 +67,7 @@
 use function in_array;
 use function is_array;
 use function is_object;
+use function is_scalar;
 use function reset;
 use function spl_object_id;
 use function sprintf;
@@ -1565,7 +1566,19 @@ final public static function getIdHashByIdentifier(array $identifier): string
 
         return implode(
             ' ',
-            $identifier,
+            array_map(
+                static function ($value) {
+                    if (! is_scalar($value) && ! ($value instanceof Stringable)) {
+                        throw new UnexpectedValueException(sprintf(
+                            'Unexpected identifier value: Expecting scalar or Stringable, got %s.',
+                            get_debug_type($value),
+                        ));
+                    }
+
+                    return $value;
+                },
+                $identifier,
+            ),
         );
     }
 
diff --git a/tests/Tests/ORM/Functional/IdentifierFunctionalTest.php b/tests/Tests/ORM/Functional/IdentifierFunctionalTest.php
new file mode 100644
index 0000000000..7f5e4952f5
--- /dev/null
+++ b/tests/Tests/ORM/Functional/IdentifierFunctionalTest.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\Tests\ORM\Functional;
+
+use Doctrine\Tests\Models\CMS\CmsUser;
+use Doctrine\Tests\OrmFunctionalTestCase;
+use UnexpectedValueException;
+
+class IdentifierFunctionalTest extends OrmFunctionalTestCase
+{
+    protected function setUp(): void
+    {
+        $this->useModelSet('cms');
+
+        parent::setUp();
+    }
+
+    public function testIdentifierArrayValue(): void
+    {
+        $this->expectException(UnexpectedValueException::class);
+        $this->expectExceptionMessage('Unexpected identifier value: Expecting scalar or Stringable, got array.');
+        $this->_em->find(CmsUser::class, ['id' => ['array']]);
+    }
+}