diff --git a/src/Illuminate/Database/Eloquent/Factories/Factory.php b/src/Illuminate/Database/Eloquent/Factories/Factory.php
index 0210fa4293b1..191e8d3d11f2 100644
--- a/src/Illuminate/Database/Eloquent/Factories/Factory.php
+++ b/src/Illuminate/Database/Eloquent/Factories/Factory.php
@@ -471,7 +471,7 @@ protected function expandAttributes(array $definition)
         return collect($definition)
             ->map($evaluateRelations = function ($attribute) {
                 if ($attribute instanceof self) {
-                    $attribute = $this->getRandomRecycledModel($attribute->modelName())
+                    $attribute = $this->getRandomRecycledModel($attribute->modelName())?->getKey()
                         ?? $attribute->recycle($this->recycle)->create()->getKey();
                 } elseif ($attribute instanceof Model) {
                     $attribute = $attribute->getKey();
diff --git a/tests/Database/DatabaseEloquentFactoryTest.php b/tests/Database/DatabaseEloquentFactoryTest.php
index c35017eb6133..b46051ac0272 100644
--- a/tests/Database/DatabaseEloquentFactoryTest.php
+++ b/tests/Database/DatabaseEloquentFactoryTest.php
@@ -898,7 +898,7 @@ public function definition()
         return [
             'commentable_id' => FactoryTestPostFactory::new(),
             'commentable_type' => FactoryTestPost::class,
-            'user_id' => FactoryTestUserFactory::new(),
+            'user_id' => fn () => FactoryTestUserFactory::new(),
             'body' => $this->faker->name(),
         ];
     }