diff --git a/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php b/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php
index e70378c6b078..ff89a5dffbc5 100644
--- a/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php
+++ b/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php
@@ -834,22 +834,12 @@ protected function setClassCastableAttribute($key, $value)
     {
         $caster = $this->resolveCasterClass($key);
 
-        if (is_null($value)) {
-            $this->attributes = array_merge($this->attributes, array_map(
-                function () {
-                },
-                $this->normalizeCastClassResponse($key, $caster->set(
-                    $this, $key, $this->{$key}, $this->attributes
-                ))
-            ));
-        } else {
-            $this->attributes = array_merge(
-                $this->attributes,
-                $this->normalizeCastClassResponse($key, $caster->set(
-                    $this, $key, $value, $this->attributes
-                ))
-            );
-        }
+        $this->attributes = array_merge(
+            $this->attributes,
+            $this->normalizeCastClassResponse($key, $caster->set(
+                $this, $key, $value, $this->attributes
+            ))
+        );
 
         if ($caster instanceof CastsInboundAttributes || ! is_object($value)) {
             unset($this->classCastCache[$key]);
diff --git a/tests/Integration/Database/EloquentModelCustomCastingTest.php b/tests/Integration/Database/EloquentModelCustomCastingTest.php
new file mode 100644
index 000000000000..39cf55454fff
--- /dev/null
+++ b/tests/Integration/Database/EloquentModelCustomCastingTest.php
@@ -0,0 +1,263 @@
+<?php
+
+namespace Illuminate\Tests\Integration\Database;
+
+use Illuminate\Contracts\Database\Eloquent\CastsAttributes;
+use Illuminate\Database\Capsule\Manager as DB;
+use Illuminate\Database\Eloquent\Model as Eloquent;
+use Illuminate\Database\Schema\Blueprint;
+use InvalidArgumentException;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @group integration
+ */
+class EloquentModelCustomCastingTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        $db = new DB;
+
+        $db->addConnection([
+            'driver' => 'sqlite',
+            'database' => ':memory:',
+        ]);
+
+        $db->bootEloquent();
+        $db->setAsGlobal();
+
+        $this->createSchema();
+    }
+
+    /**
+     * Setup the database schema.
+     *
+     * @return void
+     */
+    public function createSchema()
+    {
+        $this->schema()->create('casting_table', function (Blueprint $table) {
+            $table->increments('id');
+            $table->string('address_line_one');
+            $table->string('address_line_two');
+            $table->string('string_field');
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Tear down the database schema.
+     *
+     * @return void
+     */
+    protected function tearDown(): void
+    {
+        $this->schema()->drop('casting_table');
+    }
+
+    /**
+     * Tests...
+     */
+    public function testSavingCastedAttributesToDatabase()
+    {
+        /** @var \Illuminate\Tests\Integration\Database\CustomCasts $model */
+        $model = CustomCasts::create([
+            'address' => new AddressModel('address_line_one_value', 'address_line_two_value'),
+            'string_field' => null,
+        ]);
+
+        $this->assertSame('address_line_one_value', $model->getOriginal('address_line_one'));
+        $this->assertSame('address_line_one_value', $model->getAttribute('address_line_one'));
+
+        $this->assertSame('address_line_two_value', $model->getOriginal('address_line_two'));
+        $this->assertSame('address_line_two_value', $model->getAttribute('address_line_two'));
+
+        $this->assertSame(null, $model->getOriginal('string_field'));
+        $this->assertSame(null, $model->getAttribute('string_field'));
+        $this->assertSame('', $model->getRawOriginal('string_field'));
+
+        /** @var \Illuminate\Tests\Integration\Database\CustomCasts $another_model */
+        $another_model = CustomCasts::create([
+            'address_line_one' => 'address_line_one_value',
+            'address_line_two' => 'address_line_two_value',
+            'string_field' => 'string_value',
+        ]);
+
+        $this->assertInstanceOf(AddressModel::class, $another_model->address);
+
+        $this->assertSame('address_line_one_value', $model->address->lineOne);
+        $this->assertSame('address_line_two_value', $model->address->lineTwo);
+    }
+
+    public function testInvalidArgumentExceptionOnInvalidValue()
+    {
+        /** @var \Illuminate\Tests\Integration\Database\CustomCasts $model */
+        $model = CustomCasts::create([
+            'address' => new AddressModel('address_line_one_value', 'address_line_two_value'),
+            'string_field' => 'string_value',
+        ]);
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('The given value is not an Address instance.');
+        $model->address = 'single_string';
+
+        // Ensure model values remain unchanged
+        $this->assertSame('address_line_one_value', $model->address->lineOne);
+        $this->assertSame('address_line_two_value', $model->address->lineTwo);
+    }
+
+    public function testInvalidArgumentExceptionOnNull()
+    {
+        /** @var \Illuminate\Tests\Integration\Database\CustomCasts $model */
+        $model = CustomCasts::create([
+            'address' => new AddressModel('address_line_one_value', 'address_line_two_value'),
+            'string_field' => 'string_value',
+        ]);
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('The given value is not an Address instance.');
+        $model->address = null;
+
+        // Ensure model values remain unchanged
+        $this->assertSame('address_line_one_value', $model->address->lineOne);
+        $this->assertSame('address_line_two_value', $model->address->lineTwo);
+    }
+
+    /**
+     * Get a database connection instance.
+     *
+     * @return \Illuminate\Database\Connection
+     */
+    protected function connection()
+    {
+        return Eloquent::getConnectionResolver()->connection();
+    }
+
+    /**
+     * Get a schema builder instance.
+     *
+     * @return \Illuminate\Database\Schema\Builder
+     */
+    protected function schema()
+    {
+        return $this->connection()->getSchemaBuilder();
+    }
+}
+
+/**
+ * Eloquent Casts...
+ */
+class AddressCast implements CastsAttributes
+{
+    /**
+     * Cast the given value.
+     *
+     * @param  \Illuminate\Database\Eloquent\Model  $model
+     * @param  string  $key
+     * @param  mixed  $value
+     * @param  array  $attributes
+     * @return AddressModel
+     */
+    public function get($model, $key, $value, $attributes)
+    {
+        return new AddressModel(
+            $attributes['address_line_one'],
+            $attributes['address_line_two'],
+        );
+    }
+
+    /**
+     * Prepare the given value for storage.
+     *
+     * @param  \Illuminate\Database\Eloquent\Model  $model
+     * @param  string  $key
+     * @param  AddressModel  $value
+     * @param  array  $attributes
+     * @return array
+     */
+    public function set($model, $key, $value, $attributes)
+    {
+        if (! $value instanceof AddressModel) {
+            throw new InvalidArgumentException('The given value is not an Address instance.');
+        }
+
+        return [
+            'address_line_one' => $value->lineOne,
+            'address_line_two' => $value->lineTwo,
+        ];
+    }
+}
+
+class NonNullableString implements CastsAttributes
+{
+    /**
+     * Cast the given value.
+     *
+     * @param  \Illuminate\Database\Eloquent\Model  $model
+     * @param  string  $key
+     * @param  string  $value
+     * @param  array  $attributes
+     * @return string|null
+     */
+    public function get($model, $key, $value, $attributes)
+    {
+        return ($value != '') ? $value : null;
+    }
+
+    /**
+     * Prepare the given value for storage.
+     *
+     * @param  \Illuminate\Database\Eloquent\Model  $model
+     * @param  string  $key
+     * @param  string|null  $value
+     * @param  array  $attributes
+     * @return string
+     */
+    public function set($model, $key, $value, $attributes)
+    {
+        return $value ?? '';
+    }
+}
+
+/**
+ * Eloquent Models...
+ */
+class CustomCasts extends Eloquent
+{
+    /**
+     * @var string
+     */
+    protected $table = 'casting_table';
+
+    /**
+     * @var string[]
+     */
+    protected $guarded = [];
+
+    /**
+     * @var array
+     */
+    protected $casts = [
+        'address' => AddressCast::class,
+        'string_field' => NonNullableString::class,
+    ];
+}
+
+class AddressModel
+{
+    /**
+     * @var string
+     */
+    public $lineOne;
+
+    /**
+     * @var string
+     */
+    public $lineTwo;
+
+    public function __construct($address_line_one, $address_line_two)
+    {
+        $this->lineOne = $address_line_one;
+        $this->lineTwo = $address_line_two;
+    }
+}