diff --git a/README.md b/README.md
index 72a597f..9363f88 100644
--- a/README.md
+++ b/README.md
@@ -111,3 +111,11 @@ Test method `test_renamed_column()`.
 
 ---
 
+## Task 10. NULL on Foreign Key
+
+Folder `database/migrations/task10` contains migrations for countries and visitors table. Visitor may have undetected country, so country_id may be NULL. Change the visitors table migration to allow that.
+
+Test method `test_null_foreign_key()`.
+
+---
+
diff --git a/app/Models/Country.php b/app/Models/Country.php
new file mode 100644
index 0000000..fc698f5
--- /dev/null
+++ b/app/Models/Country.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+
+class Country extends Model
+{
+    use HasFactory;
+}
diff --git a/app/Models/Visitor.php b/app/Models/Visitor.php
new file mode 100644
index 0000000..a862c3d
--- /dev/null
+++ b/app/Models/Visitor.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+
+class Visitor extends Model
+{
+    use HasFactory;
+
+    protected $fillable = ['country_id', 'ip_address'];
+}
diff --git a/database/migrations/task10/2021_11_09_090752_create_countries_table.php b/database/migrations/task10/2021_11_09_090752_create_countries_table.php
new file mode 100644
index 0000000..41702a1
--- /dev/null
+++ b/database/migrations/task10/2021_11_09_090752_create_countries_table.php
@@ -0,0 +1,32 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+class CreateCountriesTable extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::create('countries', function (Blueprint $table) {
+            $table->id();
+            $table->string('name');
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::dropIfExists('countries');
+    }
+}
diff --git a/database/migrations/task10/2021_11_09_090858_create_visitors_table.php b/database/migrations/task10/2021_11_09_090858_create_visitors_table.php
new file mode 100644
index 0000000..7a53968
--- /dev/null
+++ b/database/migrations/task10/2021_11_09_090858_create_visitors_table.php
@@ -0,0 +1,34 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+class CreateVisitorsTable extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        // TASK: edit this migration so country_id would allow NULL values
+        Schema::create('visitors', function (Blueprint $table) {
+            $table->id();
+            $table->foreignId('country_id')->constrained();
+            $table->string('ip_address');
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::dropIfExists('visitors');
+    }
+}
diff --git a/tests/Feature/MigrationsTest.php b/tests/Feature/MigrationsTest.php
index 1499022..538ef40 100644
--- a/tests/Feature/MigrationsTest.php
+++ b/tests/Feature/MigrationsTest.php
@@ -7,6 +7,7 @@ use App\Models\Company;
 use App\Models\Product;
 use App\Models\Project;
 use App\Models\User;
+use App\Models\Visitor;
 use Illuminate\Database\QueryException;
 use Illuminate\Support\Facades\Artisan;
 use Illuminate\Support\Facades\DB;
@@ -112,4 +113,12 @@ class MigrationsTest extends TestCase
         Company::create(['name' => 'First']);
         $this->assertDatabaseHas(Company::class, ['name' => 'First']);
     }
+
+    public function test_null_foreign_key()
+    {
+        Artisan::call('migrate:fresh', ['--path' => '/database/migrations/task10']);
+
+        Visitor::create(['ip_address' => '127.0.0.1']);
+        $this->assertDatabaseCount(Visitor::class, 1);
+    }
 }