diff --git a/core/core.services.yml b/core/core.services.yml
index f44783f..47f5c19 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -1179,7 +1179,8 @@ services:
     alias: plugin.manager.element_info
   file.mime_type.mapper:
     class: Drupal\Core\File\MimeType\MimeTypeMapper
-    arguments: ['@module_handler']
+    calls:
+      - [alterMapping, ['@module_handler']]
   file.mime_type.guesser:
     class: Drupal\Core\File\MimeType\MimeTypeGuesser
     tags:
diff --git a/core/lib/Drupal/Core/File/MimeType/MimeTypeMapper.php b/core/lib/Drupal/Core/File/MimeType/MimeTypeMapper.php
index 8962393..680e94d 100644
--- a/core/lib/Drupal/Core/File/MimeType/MimeTypeMapper.php
+++ b/core/lib/Drupal/Core/File/MimeType/MimeTypeMapper.php
@@ -863,57 +863,34 @@ class MimeTypeMapper implements MimeTypeMapperInterface {
   );
 
   /**
-   * Track if mapping has been altered already.
-   *
-   * @see hook_file_mimetype_mapping_alter()
+   * Track if mapping has been already altered by modules.
    *
    * @var bool
    */
   protected $isMappingAltered = FALSE;
 
   /**
-   * The module handler.
-   *
-   * @var \Drupal\Core\Extension\ModuleHandlerInterface
-   */
-  protected $moduleHandler;
-
-  /**
-   * Constructs a new MimeTypeMapper.
-   *
-   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
-   *   The module handler.
+   * {@inheritdoc}
    */
-  public function __construct(ModuleHandlerInterface $module_handler) {
-    $this->moduleHandler = $module_handler;
+  public function alterMapping(ModuleHandlerInterface $module_handler) {
+    if (!$this->isMappingAltered) {
+      $module_handler->alter('file_mimetype_mapping', $this);
+      $this->isMappingAltered = TRUE;
+    }
+    return $this;
   }
 
   /**
    * Returns the mapping from file extensions to appropriate MIME types.
    *
-   * Invokes hook_file_mimetype_mapping_alter() to allow modules to alter
-   * the mapping.
-   *
    * @return array
    *   An array consisting of two arrays:
    *     - mimetypes: MIME types, keyed by a unique number.
    *     - extensions: an associative array with the MIME type key numbers as
    *       values. The keys are file extensions, in lower case and without any
    *       preceding dot.
-   *
-   * @see hook_file_mimetype_mapping_alter()
    */
   protected function getMapping() {
-    static $altering = FALSE;
-
-    // Allow modules to alter the default mapping.
-    if (!$this->isMappingAltered && !$altering) {
-      $altering = TRUE;
-      $this->moduleHandler->alter('file_mimetype_mapping', $this);
-      $this->isMappingAltered = TRUE;
-      $altering = FALSE;
-    }
-
     return $this->mapping;
   }
 
@@ -921,10 +898,6 @@ protected function getMapping() {
    * {@inheritdoc}
    */
   public function addMapping($mimetype, $extension) {
-    // Calls ::getMapping() to make sure new mappings are added to the
-    // ::$mapping array that has been altered by modules already.
-    $this->getMapping();
-
     if (!in_array($mimetype, $this->mapping['mimetypes'])) {
       $this->mapping['mimetypes'][] = $mimetype;
     }
@@ -938,10 +911,6 @@ public function addMapping($mimetype, $extension) {
    * {@inheritdoc}
    */
   public function removeMapping($extension) {
-    // Calls ::getMapping() to make sure mappings are removed from the
-    // ::$mapping array that has been altered by modules already.
-    $this->getMapping();
-
     $extension = strtolower($extension);
     if (isset($this->mapping['extensions'][$extension])) {
       unset($this->mapping['extensions'][$extension]);
@@ -954,10 +923,6 @@ public function removeMapping($extension) {
    * {@inheritdoc}
    */
   public function removeMimeType($mimetype) {
-    // Calls ::getMapping() to make sure mappings are removed from the
-    // ::$mapping array that has been altered by modules already.
-    $this->getMapping();
-
     if (!in_array($mimetype, $this->mapping['mimetypes'])) {
       return FALSE;
     }
diff --git a/core/lib/Drupal/Core/File/MimeType/MimeTypeMapperInterface.php b/core/lib/Drupal/Core/File/MimeType/MimeTypeMapperInterface.php
index 6772cb2..1486c00 100644
--- a/core/lib/Drupal/Core/File/MimeType/MimeTypeMapperInterface.php
+++ b/core/lib/Drupal/Core/File/MimeType/MimeTypeMapperInterface.php
@@ -6,12 +6,28 @@
 
 namespace Drupal\Core\File\MimeType;
 
+use Drupal\Core\Extension\ModuleHandlerInterface;
+
 /**
  * Provides a sensible mapping between filename extensions and MIME types.
  */
 interface MimeTypeMapperInterface {
 
   /**
+   * Allow modules to alter the default mapping.
+   *
+   * Invokes hook_file_mimetype_mapping_alter().
+   *
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler.
+   *
+   * @return $this
+   *
+   * @see hook_file_mimetype_mapping_alter()
+   */
+  public function alterMapping(ModuleHandlerInterface $module_handler);
+
+  /**
    * Adds a mapping between a MIME type and an extension.
    *
    * @param string $mimetype