diff --git a/src/Importer.php b/src/Importer.php
index 62f3c36..664d348 100644
--- a/src/Importer.php
+++ b/src/Importer.php
@@ -128,10 +128,10 @@ class Importer implements ImporterInterface {
     $this->linkDomain = $link_domain;
     $this->accountSwitcher = $account_switcher;
 
-    $this->coreUsersUuids = [
-      0 => \Drupal::entityTypeManager()->getStorage('user')->load(0)->uuid(),
-      1 => \Drupal::entityTypeManager()->getStorage('user')->load(1)->uuid(),
-    ];
+    $coreUserUids = [0, 1];
+    $this->coreUsersUuids = array_map(function ($uid) {
+      return $this->entityTypeManager()->getStorage('user')->load($uid)->uuid();
+    }, $coreUserUids);
   }
 
   /**
@@ -142,18 +142,20 @@ class Importer implements ImporterInterface {
    * @param array $item
    *   Item to extract core user Uuids from.
    */
-  private function overrideCoreUsersUuids(&$item) {
+  protected function overrideCoreUsersUuids(&$item) {
     // If the content is from a system user, override its UUID to match the
     // one of the current site.
     $userPatternTemplate = "/user/%d?_format=hal_json";
     if ($item['_links']['type']['href'] === "http://drupal.org/rest/type/user/user") {
       foreach ($this->coreUsersUuids as $uid => $uuid) {
         $userPattern = sprintf($userPatternTemplate, $uid);
-        // Match the end of the string.
+        // Check against the pattern.
         if (strpos($item['_links']['self']['href'], $userPattern) !== FALSE) {
+          // Add the found UUID to the collection of import UUIDs, override the
+          // UUID in the import data with the UUID from the actual user.
           $overriddenUuid = $item['uuid'][0]['value'];
           $item['uuid'][0]['value'] = $uuid;
-          if (!is_array($this->coreUsersImportUuids[$uid])) {
+          if (!isset($this->coreUsersImportUuids[$uid])) {
             $this->coreUsersImportUuids[$uid] = [];
           }
           if (!in_array($overriddenUuid, $this->coreUsersImportUuids[$uid])) {
@@ -170,7 +172,7 @@ class Importer implements ImporterInterface {
    * @param string $contents
    *   Serialized content to manipulate.
    */
-  private function replaceCoreUserUuidsInString(&$contents) {
+  protected function replaceCoreUserUuidsInString(&$contents) {
     foreach ($this->coreUsersUuids as $uid => $uuid) {
       $contents = str_replace($this->coreUsersUuids[$uid], $uuid, $contents);
     }