diff --git a/core/lib/Drupal/Core/Config/FileStorage.php b/core/lib/Drupal/Core/Config/FileStorage.php
index 78a1af6753b77f93c97cb9b1adcd0b1cf3d8e9f1..1e22fdc4116e040182b94489801c430ff5681eb2 100644
--- a/core/lib/Drupal/Core/Config/FileStorage.php
+++ b/core/lib/Drupal/Core/Config/FileStorage.php
@@ -53,7 +53,7 @@ public function __construct($directory) {
    *   The path to the configuration file.
    */
   public function getFilePath($name) {
-    return $this->directory . '/' . $name . '.' . self::getFileExtension();
+    return $this->directory . '/' . $name . '.' . static::getFileExtension();
   }
 
   /**
@@ -189,7 +189,7 @@ public function listAll($prefix = '') {
     if (!file_exists($this->directory)) {
       throw new StorageException($this->directory . '/ not found.');
     }
-    $extension = '.' . self::getFileExtension();
+    $extension = '.' . static::getFileExtension();
     $files = glob($this->directory . '/' . $prefix . '*' . $extension);
     $clean_name = function ($value) use ($extension) {
       return basename($value, $extension);
diff --git a/core/lib/Drupal/Core/Config/InstallStorage.php b/core/lib/Drupal/Core/Config/InstallStorage.php
index f232f635d084ff07c9021d5ebb99fdb2c37509c3..eceef0162607340261f15af1407d7519bad6f838 100644
--- a/core/lib/Drupal/Core/Config/InstallStorage.php
+++ b/core/lib/Drupal/Core/Config/InstallStorage.php
@@ -44,7 +44,7 @@ public function getFilePath($name) {
     $path = FALSE;
     foreach (array('profile', 'module', 'theme') as $type) {
       if ($path = drupal_get_path($type, $owner)) {
-        $file = $path . '/config/' . $name . '.' . self::getFileExtension();
+        $file = $path . '/config/' . $name . '.' . static::getFileExtension();
         if (file_exists($file)) {
           return $file;
         }