diff --git a/core/modules/user/src/PermissionHandler.php b/core/modules/user/src/PermissionHandler.php
index d8fe021..e27f1d4 100644
--- a/core/modules/user/src/PermissionHandler.php
+++ b/core/modules/user/src/PermissionHandler.php
@@ -80,7 +80,7 @@ class PermissionHandler implements PermissionHandlerInterface {
    *
    * @var array
    */
-  protected $permisisonsCache;
+  protected $permissionsCache;
 
   /**
    * Constructs a new PermissionHandler.
@@ -103,14 +103,25 @@ public function __construct(ModuleHandlerInterface $module_handler, TranslationI
   /**
    * Gets the YAML discovery.
    *
+   * @param string $module_name
+   *   (optional) The module name to get YAML discovery for. If omitted, returns
+   *   YAML discovery for all modules.
+   *
    * @return \Drupal\Component\Discovery\YamlDiscovery
    *   The YAML discovery.
    */
-  protected function getYamlDiscovery() {
-    if (!isset($this->yamlDiscovery)) {
-      $this->yamlDiscovery = new YamlDiscovery('permissions', $this->moduleHandler->getModuleDirectories());
+  protected function getYamlDiscovery($module_name = NULL) {
+    if (!isset($this->yamlDiscovery[$module_name])) {
+      $directories = $this->moduleHandler->getModuleDirectories();
+      if ($module_name) {
+        // Just discover the single module.
+        if (!empty($directories[$module_name])) {
+          $directories = [$module_name => $directories[$module_name]];
+        }
+      }
+      $this->yamlDiscovery[$module_name] = new YamlDiscovery('permissions', $directories);
     }
-    return $this->yamlDiscovery;
+    return $this->yamlDiscovery[$module_name];
   }
 
   /**
@@ -126,17 +137,17 @@ public function getPermissions($module_name = NULL) {
    * {@inheritdoc}
    */
   public function moduleProvidesPermissions($module_name) {
-    if (!isset($this->permisisonsCache[$module_name])) {
+    if (!isset($this->permissionsCache[$module_name])) {
       $permissions = $this->getPermissions($module_name);
     }
-    $this->permisisonsCache[$module_name] = FALSE;
+    $this->permissionsCache[$module_name] = FALSE;
     foreach ($permissions as $permission) {
       if ($permission['provider'] == $module_name) {
-        $this->permisisonsCache[$module_name] = TRUE;
+        $this->permissionsCache[$module_name] = TRUE;
         break;
       }
     }
-    return $this->permisisonsCache[$module_name];
+    return $this->permissionsCache[$module_name];
   }
 
   /**
@@ -155,19 +166,7 @@ protected function buildPermissionsYaml($module_name = NULL) {
     $all_permissions = array();
     $all_callback_permissions = array();
 
-    if ($module_name) {
-      // Just discover the single module.
-      $directories = $this->moduleHandler->getModuleDirectories();
-      $module_directories = [];
-      if (!empty($directories[$module_name])) {
-        $module_directories = [$module_name => $directories[$module_name]];
-      }
-      $discovery = new YamlDiscovery('permissions', $module_directories);
-    }
-    else {
-      // Use the default discovery - which handles all enabled modules.
-      $discovery = $this->getYamlDiscovery();
-    }
+    $discovery = $this->getYamlDiscovery($module_name);
     foreach ($discovery->findAll() as $provider => $permissions) {
       // The top-level 'permissions_callback' is a list of methods in controller
       // syntax, see \Drupal\Core\Controller\ControllerResolver. These methods