diff --git a/core/modules/media/src/MediaTypeForm.php b/core/modules/media/src/MediaTypeForm.php
index 170a34fa5c2e71fd709e4c6010199d6efad5a0ae..7766af2e567d63be3dd65acd453ecaf0cd21d6ba 100644
--- a/core/modules/media/src/MediaTypeForm.php
+++ b/core/modules/media/src/MediaTypeForm.php
@@ -131,6 +131,13 @@ public function form(array $form, FormStateInterface $form_state) {
       '#options' => $options,
       '#description' => $source_description,
       '#ajax' => ['callback' => '::ajaxHandlerData'],
+      // Rebuilding the form as part of the AJAX request is a workaround to
+      // enforce machine_name validation.
+      // @todo This was added as part of #2932226 and it should be removed once
+      //   https://www.drupal.org/project/drupal/issues/2557299 solves it in a
+      //   more generic way.
+      '#executes_submit_callback' => TRUE,
+      '#submit' => [[static::class, 'rebuildSubmit']],
       '#required' => TRUE,
       // Once the media type is created, its source plugin cannot be changed
       // anymore.
@@ -233,6 +240,18 @@ public function form(array $form, FormStateInterface $form_state) {
     return $form;
   }
 
+  /**
+   * Form submission handler to rebuild the form on select submit.
+   *
+   * @param array $form
+   *   Full form array.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   Current form state.
+   */
+  public static function rebuildSubmit(array &$form, FormStateInterface $form_state) {
+    $form_state->setRebuild();
+  }
+
   /**
    * Prepares workflow options to be used in the 'checkboxes' form element.
    *
@@ -273,7 +292,7 @@ protected function getSourceSubFormState(array $form, FormStateInterface $form_s
   public function validateForm(array &$form, FormStateInterface $form_state) {
     parent::validateForm($form, $form_state);
 
-    if ($form['source_dependent']['source_configuration']) {
+    if (isset($form['source_dependent']['source_configuration'])) {
       // Let the selected plugin validate its settings.
       $this->entity->getSource()->validateConfigurationForm($form['source_dependent']['source_configuration'], $this->getSourceSubFormState($form, $form_state));
     }
@@ -296,7 +315,7 @@ function ($item) {
       ->setStatus((bool) $form_state->getValue(['options', 'status']))
       ->setNewRevision((bool) $form_state->getValue(['options', 'new_revision']));
 
-    if ($form['source_dependent']['source_configuration']) {
+    if (isset($form['source_dependent']['source_configuration'])) {
       // Let the selected plugin save its settings.
       $this->entity->getSource()->submitConfigurationForm($form['source_dependent']['source_configuration'], $this->getSourceSubFormState($form, $form_state));
     }
diff --git a/core/modules/media/tests/src/FunctionalJavascript/MediaTypeCreationTest.php b/core/modules/media/tests/src/FunctionalJavascript/MediaTypeCreationTest.php
index 652aca8c6be17c732feccf4c509751e5429bb138..4f491ccb4a07aabb61cb1bc0710a7177a9cd57f3 100644
--- a/core/modules/media/tests/src/FunctionalJavascript/MediaTypeCreationTest.php
+++ b/core/modules/media/tests/src/FunctionalJavascript/MediaTypeCreationTest.php
@@ -53,6 +53,15 @@ public function testMediaTypeCreationFormWithDefaultField() {
     // Check that the plugin cannot be changed after it is set on type creation.
     $assert_session->fieldDisabled('Media source');
     $assert_session->pageTextContains('The media source cannot be changed after the media type is created.');
+
+    // Check that a new type with the same machine name cannot be created.
+    $this->drupalGet('admin/structure/media/add');
+    $page->fillField('label', $label);
+    $session->wait(5000, "jQuery('.machine-name-value').text() === '{$mediaTypeMachineName}'");
+    $page->selectFieldOption('Media source', 'test');
+    $assert_session->assertWaitOnAjaxRequest();
+    $page->pressButton('Save');
+    $assert_session->pageTextContains('The machine-readable name is already in use. It must be unique.');
   }
 
   /**