diff --git a/app/Services/Option.php b/app/Services/Option.php
index 00733b6..844d212 100644
--- a/app/Services/Option.php
+++ b/app/Services/Option.php
@@ -49,8 +49,12 @@ class Option
      *
      * @return string The option value.
      */
-    public function set($key, string $value)
+    public function set($key, ?string $value)
     {
+        if (is_null($value)) {
+            $value = '';
+        }
+
         $option = $this->option->where('key', $key)->first();
 
         if ($option) {
diff --git a/tests/Unit/Services/SiteOptionTest.php b/tests/Unit/Services/SiteOptionTest.php
index 566e8ff..c2f3ae7 100644
--- a/tests/Unit/Services/SiteOptionTest.php
+++ b/tests/Unit/Services/SiteOptionTest.php
@@ -22,6 +22,17 @@ class SiteOptionTest extends TestCase
     }
 
     /** @test */
+    public function option_value_null_must_be_converted_to_empty_string()
+    {
+        Option::set('testing_key', null);
+
+        $this->seeInDatabase('site_options', [
+            'key'   => 'testing_key',
+            'value' => '',
+        ]);
+    }
+
+    /** @test */
     public function option_can_be_get()
     {
         \DB::table('site_options')->insert([