diff --git a/core/modules/aggregator/aggregator.module b/core/modules/aggregator/aggregator.module
index bee7504..2b91136 100644
--- a/core/modules/aggregator/aggregator.module
+++ b/core/modules/aggregator/aggregator.module
@@ -44,8 +44,6 @@ function aggregator_help($path, $arg) {
       return '<p>' . t('Categories allow feed items from different feeds to be grouped together. For example, several sport-related feeds may belong to a category named <em>Sports</em>. Feed items may be grouped automatically (by selecting a category when creating or editing a feed) or manually (via the <em>Categorize</em> page available from feed item listings). Each category provides its own feed page and block.') . '</p>';
     case 'admin/config/services/aggregator/add/opml':
       return '<p>' . t('<acronym title="Outline Processor Markup Language">OPML</acronym> is an XML format used to exchange multiple feeds between aggregators. A single OPML document may contain a collection of many feeds. Drupal can parse such a file and import all feeds at once, saving you the effort of adding them manually. You may either upload a local file from your computer or enter a URL where Drupal can download it.') . '</p>';
-    case 'admin/config/services/aggregator/delete':
-      return;
   }
 }
 
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/CategoryStorageController.php b/core/modules/aggregator/lib/Drupal/aggregator/CategoryStorageController.php
index 81e2af3..0eab4df 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/CategoryStorageController.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/CategoryStorageController.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * @file
  * Contains \Drupal\aggregator\CategoryStorageController.
@@ -76,5 +77,18 @@ public function delete($cid) {
       ->execute();
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function isUnique($title, $cid = NULL) {
+    $query = $this->database->select('aggregator_category', 'ac')
+      ->fields('ac', array('title'))
+      ->condition('title', $title);
+    if (!empty($cid)) {
+      $query->condition('cid', $cid, '<>');
+    }
+    $rows = $query->execute()->fetchColumn();
+    return (empty($rows));
+  }
 
 }
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/CategoryStorageControllerInterface.php b/core/modules/aggregator/lib/Drupal/aggregator/CategoryStorageControllerInterface.php
index b47f9c4..3d829ac 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/CategoryStorageControllerInterface.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/CategoryStorageControllerInterface.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * @file
  * Contains \Drupal\aggregator\CategoryStorageControllerInterface.
@@ -49,4 +50,20 @@ public function update(array $category);
    */
   public function delete($cid);
 
+  /**
+   * Checks if the category title is unique.
+   *
+   * Optionally passes a category ID to exclude, if this check is for an
+   * existing category.
+   *
+   * @param string $title
+   *   The category title.
+   * @param int $cid
+   *   (optional) The category ID to exclude from the check.
+   *
+   * @return bool
+   *   TRUE if the category title is unique, FALSE otherwise.
+   */
+  public function isUnique($title, $cid = NULL);
 }
+
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Form/CategoryAdminForm.php b/core/modules/aggregator/lib/Drupal/aggregator/Form/CategoryAdminForm.php
index 414633a..5cf3758 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Form/CategoryAdminForm.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Form/CategoryAdminForm.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * @file
  * Contains Drupal\aggregator\Form\CategoryAdminForm.
@@ -13,6 +14,7 @@
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Form\FormInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\Request;
 
 /**
  * Provides a form for configuring aggregator categories.
@@ -41,6 +43,13 @@ class CategoryAdminForm implements FormInterface, ControllerInterface {
   protected $categoryStorageController;
 
   /**
+   * The current request.
+   *
+   * @var \Symfony\Component\HttpFoundation\Request
+   */
+  protected $request;
+
+  /**
    * Creates a new CategoryForm object.
    *
    * @param \Drupal\Core\Database\Connection $database
@@ -77,7 +86,8 @@ public function getFormID() {
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, array &$form_state, $cid = NULL) {
+  public function buildForm(array $form, array &$form_state, $cid = NULL, Request $request = NULL) {
+    $this->request = $request;
     $category = (object) $this->categoryStorageController->load($cid);
     $form['title'] = array(
       '#type' => 'textfield',
@@ -92,9 +102,15 @@ public function buildForm(array $form, array &$form_state, $cid = NULL) {
       '#default_value' => isset($category->description) ? $category->description : '',
     );
     $form['actions'] = array('#type' => 'actions');
-    $form['actions']['submit'] = array('#type' => 'submit', '#value' => t('Save'));
+    $form['actions']['submit'] = array(
+      '#type' => 'submit',
+      '#value' => t('Save'),
+    );
     if (!empty($category->cid)) {
-      $form['actions']['delete'] = array('#type' => 'submit', '#value' => t('Delete'));
+      $form['actions']['delete'] = array(
+        '#type' => 'submit',
+        '#value' => t('Delete'),
+      );
       $form['cid'] = array('#type' => 'hidden', '#value' => $category->cid);
     }
 
@@ -107,14 +123,16 @@ public function buildForm(array $form, array &$form_state, $cid = NULL) {
   public function validateForm(array &$form, array &$form_state) {
     if ($form_state['values']['op'] == t('Save')) {
       // Check for duplicate titles.
+      $title = $form_state['values']['title'];
       if (isset($form_state['values']['cid'])) {
-        $category = $this->database->query("SELECT cid FROM {aggregator_category} WHERE title = :title AND cid <> :cid", array(':title' => $form_state['values']['title'], ':cid' => $form_state['values']['cid']))->fetchObject();
+        // Exclude the current category ID when checking if it's unique.
+        $unique = $this->categoryStorageController->isUnique($title, $form_state['values']['cid']);
       }
       else {
-        $category = $this->database->query("SELECT cid FROM {aggregator_category} WHERE title = :title", array(':title' => $form_state['values']['title']))->fetchObject();
+        $unique = $this->categoryStorageController->isUnique($title);
       }
-      if ($category) {
-        form_set_error('title', t('A category named %category already exists. Enter a unique title.', array('%category' => $form_state['values']['title'])));
+      if (!$unique) {
+        form_set_error('title', t('A category named %category already exists. Enter a unique title.', array('%category' => $title)));
       }
     }
   }
@@ -142,7 +160,12 @@ public function submitForm(array &$form, array &$form_state) {
       $cid = $form_state['values']['cid'];
       $this->categoryStorageController->update($form_state['values']);
       drupal_set_message(t('The category %category has been updated.', array('%category' => $title)));
-      $form_state['redirect'] = arg(0) == 'admin' ? 'admin/config/services/aggregator/' : 'aggregator/categories/' . $cid;
+      if (preg_match('/^\/admin/', $this->request->getPathInfo())) {
+        $form_state['redirect'] = 'admin/config/services/aggregator/';
+      }
+      else {
+        $form_state['redirect'] = 'aggregator/categories/' . $cid;
+      }
       $this->updateMenuLink('update', $link_path . $cid, $title);
       return;
     }
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Form/CategoryDeleteForm.php b/core/modules/aggregator/lib/Drupal/aggregator/Form/CategoryDeleteForm.php
index bb46850..474e499 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Form/CategoryDeleteForm.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Form/CategoryDeleteForm.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * @file
  * Contains \Drupal\aggregator\Form\CategoryDeleteForm.
@@ -50,6 +51,11 @@ class CategoryDeleteForm extends ConfirmFormBase implements ControllerInterface
   protected $categoryStorageController;
 
   /**
+   * @var
+   */
+  protected $request;
+
+  /**
    * Creates a new CategoryDeleteForm.
    *
    * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
@@ -135,6 +141,7 @@ public function buildForm(array $form, array &$form_state, Request $request = NU
       throw new NotFoundHttpException();
     }
     $this->category = $category;
+    $this->request = $request;
     return parent::buildForm($form, $form_state, $request);
   }
 
@@ -149,7 +156,12 @@ public function submitForm(array &$form, array &$form_state) {
     $this->deleteBlocks($cid);
     watchdog('aggregator', 'Category %category deleted.', array('%category' => $title));
     drupal_set_message(t('The category %category has been deleted.', array('%category' => $title)));
-    $form_state['redirect'] = arg(0) == 'admin' ? 'admin/config/services/aggregator' : 'aggregator';
+    if (preg_match('/^\/admin/', $this->request->getPathInfo())) {
+      $form_state['redirect'] = 'admin/config/services/aggregator/';
+    }
+    else {
+      $form_state['redirect'] = 'aggregator';
+    }
     $this->updateMenuLink('delete', 'aggregator/categories/' . $cid, $title);
   }