diff --git a/config/schema/widget.schema.yml b/config/schema/widget.schema.yml
new file mode 100644
index 0000000..e410d18
--- /dev/null
+++ b/config/schema/widget.schema.yml
@@ -0,0 +1,54 @@
+# Block settings schema.
+block.settings.widget_block:
+  type: block_settings
+  label: 'Widget block'
+  mapping:
+    blocks:
+      type: sequence
+      label: 'Blocks'
+      sequence:
+        - type: widget_block.block
+    layout:
+      type: string
+      label: 'Layout'
+    classes:
+      type: sequence
+      label: 'Classes'
+      sequence:
+        - type: string
+    regions:
+      type: sequence
+      label: 'Regions'
+      sequence:
+        - type: widget_block.region
+
+widget_block.block:
+  type: block.settings.[id]
+  label: 'Widget block settings'
+  mapping:
+    id:
+      type: string
+      label: 'Id'
+    region:
+      type: string
+      label: 'Region'
+
+widget_block.region:
+  type: mapping
+  label: 'Widget region settings'
+  mapping:
+    id:
+      type: string
+      label: 'Id'
+    region_id:
+      type: string
+      label: 'Region id'
+    label:
+      type: string
+      label: 'Label'
+    weight:
+      type: integer
+      label: 'Weight'
+    uuid:
+      type: string
+      label: 'Uuid'
diff --git a/src/Plugin/Block/WidgetBlock.php b/src/Plugin/Block/WidgetBlock.php
index 96cf1b2..4c8f087 100644
--- a/src/Plugin/Block/WidgetBlock.php
+++ b/src/Plugin/Block/WidgetBlock.php
@@ -154,10 +154,6 @@ public function build() {
    */
   public function blockForm($form, FormStateInterface $form_state) {
     // Fish the page object from the form args.
-
-    // Prevent serialization error.
-    $form['admin_label']['#markup'] = (string) $form['admin_label']['#markup'];
-
     foreach ($form_state->getBuildInfo()['args'] as $arg) {
       if ($arg instanceof Page) {
         $this->page = $arg->getExecutable();
@@ -174,7 +170,7 @@ public function blockForm($form, FormStateInterface $form_state) {
 
     $widget_blocks = $form_state->hasValue(array('settings', 'blocks')) ? $form_state->getValue(array('settings', 'blocks')) : $this->configuration['blocks'];
     $layout = $form_state->hasValue(array('settings', 'layout')) ? $form_state->getValue(array('settings', 'layout')) : $this->configuration['layout'];
-    $classes = $form_state->hasValue(array('settings', 'classes')) ? $form_state->getValue(array('settings', 'classes')) : $this->configuration['classes'];
+    $classes = $form_state->hasValue(array('settings', 'classes')) && !empty($form_state->getValue(array('settings', 'classes'))) ? $form_state->getValue(array('settings', 'classes')) : $this->configuration['classes'];
 
     $ajax_properties = array(
       '#ajax' => array(
@@ -210,7 +206,8 @@ public function blockForm($form, FormStateInterface $form_state) {
     $form['classes'] = array(
       '#type' => 'textfield',
       '#title' => t('CSS Classes'),
-      '#default_value' => $classes,
+      '#default_value' => implode(", ", $this->configuration['classes']),
+      '#description' => t("A list of CSS Classes that will be applied in the widget. Put each on comma separated."),
     );
 
     if (!$layout) {
@@ -269,7 +266,7 @@ public function blockForm($form, FormStateInterface $form_state) {
   public function blockSubmit($form, FormStateInterface $form_state) {
     $this->configuration['blocks'] = array();
     $this->configuration['layout'] = $form_state->getValue('layout');
-    $this->configuration['classes'] = $form_state->getValue('classes');
+    $this->configuration['classes'] = array_filter(explode(",", $form_state->getValue('classes')), 'trim');
     // Set empty block ID's to NULL.
     foreach ($form_state->getValue('blocks') as $region_id => $block) {
       if (!empty($block['id'])) {
diff --git a/src/Tests/WidgetBlockTest.php b/src/Tests/WidgetBlockTest.php
new file mode 100644
index 0000000..fe137ee
--- /dev/null
+++ b/src/Tests/WidgetBlockTest.php
@@ -0,0 +1,59 @@
+<?php
+/**
+ * @file
+ * Contains \Drupal\widget\Tests\WidgetBlockTest.
+ */
+
+namespace Drupal\widget\Tests;
+
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Generic widget block tests.
+ *
+ * @group widget
+ */
+class WidgetBlockTest extends WebTestBase {
+
+  public static $modules = [
+    'block',
+    'layout',
+    'ctools',
+    'page_manager',
+    'page_layout',
+    'widget',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    parent::setUp();
+    $this->drupalPlaceBlock('widget_block');
+    $admin = $this->drupalCreateUser([
+      'administer blocks',
+      'administer pages',
+    ], $this->randomMachineName(), TRUE);
+    $this->drupalLogin($admin);
+  }
+
+  /**
+   * Tests a form without submit handler.
+   */
+  public function testFormNoSubmitHandler() {
+    $edit = [
+      'settings[layout]' => 'widget_1col',
+    ];
+    $this->drupalPostAjaxForm('admin/structure/block/add/widget_block/classy?region=content', $edit, 'settings[layout]');
+    $edit = [
+      'settings[layout]' => 'widget_1col',
+      'settings[blocks][links][id]' => 'system_menu_block:main',
+      'settings[blocks][main][id]' => 'system_main_block',
+    ];
+    $this->drupalPostForm(NULL, $edit, 'Save block');
+    $this->assertText(t('The block configuration has been saved.'));
+    $this->drupalPlaceBlock('widget_block');
+    $this->drupalGet('<front>');
+  }
+
+}