diff -u b/src/Plugin/Block/MenuBlock.php b/src/Plugin/Block/MenuBlock.php
--- b/src/Plugin/Block/MenuBlock.php
+++ b/src/Plugin/Block/MenuBlock.php
@@ -3,15 +3,15 @@
 namespace Drupal\menu_block\Plugin\Block;
 
 use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Menu\MenuActiveTrailInterface;
+use Drupal\Core\Menu\MenuLinkTreeInterface;
+use Drupal\Core\Menu\MenuTreeParameters;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\system\Entity\Menu;
 use Drupal\system\Plugin\Block\SystemMenuBlock;
 use Symfony\Component\DependencyInjection\ContainerInterface;
-use Drupal\Core\Entity\EntityTypeManagerInterface;
-use Drupal\Core\Menu\MenuActiveTrailInterface;
-use Drupal\Core\Menu\MenuLinkTreeInterface;
-use Drupal\Core\Menu\MenuTreeParameters;
 
 /**
  * Provides an extended Menu block.
@@ -188,7 +188,6 @@
     $this->configuration['expand'] = $form_state->getValue('expand');
     $this->configuration['parent'] = $form_state->getValue('parent');
     $this->configuration['suggestion'] = $form_state->getValue('suggestion');
-    $this->configuration['label_type'] = $form_state->getValue('label_type');
   }
 
   /**
@@ -216,6 +215,7 @@
     $this->configuration['expand'] = $form_state->getValue('expand');
     $this->configuration['parent'] = $form_state->getValue('parent');
     $this->configuration['suggestion'] = $form_state->getValue('suggestion');
+    $this->configuration['label_type'] = $form_state->getValue('label_type');
   }
 
   /**
@@ -298,7 +298,6 @@
       'expand' => 0,
       'parent' => $this->getDerivativeId() . ':',
       'suggestion' => strtr($this->getDerivativeId(), '-', '_'),
-      'label_type' => self::LABEL_BLOCK,
     ];
   }
 
@@ -364,6 +363,7 @@
       'expand' => 0,
       'parent' => $this->getDerivativeId() . ':',
       'suggestion' => strtr($this->getDerivativeId(), '-', '_'),
+      'label_type' => self::LABEL_BLOCK,
     ];
   }
 
@@ -378,7 +378,7 @@
   }
 
   /**
-   * Get the configured block label.
+   * Gets the configured block label.
    *
    * @return string
    *   The configured label.
@@ -406,10 +406,10 @@
   }
 
   /**
-   * Get the label of the configured menu.
+   * Gets the label of the configured menu.
    *
    * @return string|null
-   *   Menu label or null if no menu exists.
+   *   Menu label or NULL if no menu exists.
    */
   protected function getMenuTitle() {
     try {
@@ -424,7 +424,10 @@
   }
 
   /**
-   * @return string
+   * Gets the title of a fixed parent item.
+   *
+   * @return string|null
+   *   Title of the configured (fixed) parent item, or NULL if there is none.
    */
   protected function getFixedParentItemTitle() {
     $parent = $this->configuration['parent'];
@@ -436,12 +439,13 @@
   }
 
   /**
-   * Get the active menu item's title.
+   * Gets the active menu item's title.
    *
-   * @return string
-   *   Current menu item title.
+   * @return string|null
+   *   Currently active menu item title or NULL if there's nothing active.
    */
   protected function getActiveItemTitle() {
+    /** @var array $active_trail_ids */
     $active_trail_ids = $this->getDerivativeActiveTrailIds();
     if ($active_trail_ids) {
       return $this->getLinkTitleFromLink(reset($active_trail_ids));
@@ -449,14 +453,15 @@
   }
 
   /**
-   * Get the current menu item's parent menu title.
+   * Gets the title of the parent of the active menu item.
    *
-   * @return string
-   *   The menu item title.
+   * @return string|null
+   *   The title of the parent of the active menu item, the title of the active
+   *   item if it has no parent, or NULL if there's no active menu item.
    */
   protected function getActiveTrailParentTitle() {
+    /** @var array $active_trail_ids */
     $active_trail_ids = $this->getDerivativeActiveTrailIds();
-
     if ($active_trail_ids) {
       if (count($active_trail_ids) === 1) {
         return $this->getActiveItemTitle();
@@ -466,12 +471,13 @@
   }
 
   /**
-   * Get the current menu item's root menu item title.
+   * Gets the current menu item's root menu item title.
    *
-   * @return string
-   *   The menu item title.
+   * @return string|null
+   *   The root menu item title or NULL if there's no active item.
    */
   protected function getActiveTrailRootTitle() {
+    /** @var array $active_trail_ids */
     $active_trail_ids = $this->getDerivativeActiveTrailIds();
 
     if ($active_trail_ids) {
@@ -480,10 +486,10 @@
   }
 
   /**
-   * Get an array of the active trail menu link items.
+   * Gets an array of the active trail menu link items.
    *
    * @return array
-   *   The active trail.
+   *   The active trail menu item IDs.
    */
   protected function getDerivativeActiveTrailIds() {
     $menu_id = $this->getDerivativeId();
@@ -491,32 +497,33 @@
   }
 
   /**
-   * Given a menu item ID, get that item's title.
+   * Gets the title of a given menu item ID.
    *
    * @param string $link_id
-   *   Menu Item ID.
+   *   The menu item ID.
    *
-   * @return string
-   *   The menu item title.
+   * @return string|null
+   *   The menu item title or NULL if the given menu item can't be found.
    */
   protected function getLinkTitleFromLink($link_id) {
     $parameters = new MenuTreeParameters();
     $menu = $this->menuTree->load($this->getDerivativeId(), $parameters);
-    if ($link = $this->findLinkInTree($menu, $link_id)) {
+    $link = $this->findLinkInTree($menu, $link_id);
+    if ($link) {
       return $link->link->getTitle();
     }
   }
 
   /**
-   * Find and return the menu link item from the menu tree.
+   * Gets the menu link item from the menu tree.
    *
    * @param array $menu_tree
    *   Associative array containing the menu link tree data.
    * @param string $link_id
    *   Menu link id to find.
    *
-   * @return \Drupal\Core\Menu\MenuLinkTreeElement
-   *   The link element from the given menu tree.
+   * @return \Drupal\Core\Menu\MenuLinkTreeElement|null
+   *   The link element from the given menu tree or NULL if it can't be found.
    */
   protected function findLinkInTree(array $menu_tree, $link_id) {
     if (isset($menu_tree[$link_id])) {
@@ -524,7 +531,8 @@
     }
     /** @var \Drupal\Core\Menu\MenuLinkTreeElement $link */
     foreach ($menu_tree as $link) {
-      if ($link = $this->findLinkInTree($link->subtree, $link_id)) {
+      $link = $this->findLinkInTree($link->subtree, $link_id);
+      if ($link) {
         return $link;
       }
     }