diff -u b/core/modules/language/tests/src/Kernel/LanguageDisplayConfigurationAfterUninstallTest.php b/core/modules/language/tests/src/Kernel/LanguageDisplayConfigurationAfterUninstallTest.php
--- b/core/modules/language/tests/src/Kernel/LanguageDisplayConfigurationAfterUninstallTest.php
+++ b/core/modules/language/tests/src/Kernel/LanguageDisplayConfigurationAfterUninstallTest.php
@@ -2,6 +2,8 @@
 
 namespace Drupal\Tests\language\Kernel;
 
+use Drupal\Core\Entity\Entity\EntityFormDisplay;
+use Drupal\Core\Entity\Entity\EntityFormMode;
 use Drupal\KernelTests\KernelTestBase;
 use Drupal\Core\Entity\Entity\EntityViewDisplay;
 use Drupal\Core\Entity\Entity\EntityViewMode;
@@ -33,9 +35,27 @@
     // For uninstall to work.
     $this->installSchema('user', ['users_data']);
 
-    // Create default display.
+    // Create 'default' view-display.
+    $display = EntityViewDisplay::create([
+      'targetEntityType' => 'entity_test',
+      'bundle' => 'entity_test',
+      'mode' => 'default',
+      'status' => TRUE,
+    ]);
+    $display->save();
+
+    // Create 'default' form-display.
+    $display = EntityFormDisplay::create([
+      'targetEntityType' => 'entity_test',
+      'bundle' => 'entity_test',
+      'mode' => 'default',
+      'status' => TRUE,
+    ]);
+    $display->save();
+
+    // Create a view-mode 'manual', create view-display that uses it.
     EntityViewMode::create([
-      'id' => 'entity_test.default',
+      'id' => 'entity_test.manual',
       'targetEntityType' => 'entity_test',
       'status' => TRUE,
       'enabled' => TRUE,
@@ -43,7 +63,22 @@
     $display = EntityViewDisplay::create([
       'targetEntityType' => 'entity_test',
       'bundle' => 'entity_test',
-      'mode' => 'default',
+      'mode' => 'manual',
+      'status' => TRUE,
+    ]);
+    $display->save();
+
+    // Create a new form-mode 'manual', create form-display that uses it.
+    EntityFormMode::create([
+      'id' => 'entity_test.manual',
+      'targetEntityType' => 'entity_test',
+      'status' => TRUE,
+      'enabled' => TRUE,
+    ])->save();
+    $display = EntityFormDisplay::create([
+      'targetEntityType' => 'entity_test',
+      'bundle' => 'entity_test',
+      'mode' => 'manual',
       'status' => TRUE,
     ]);
     $display->save();
@@ -51,19 +86,28 @@
   }
 
   /**
-   * Tests the widget with the locked languages.
+   * Tests display configuration after uninstalling Language module.
    */
   public function testConfigAfterUninstall() {
-    $default_config_name = 'core.entity_view_display.entity_test.entity_test.default';
+    $default_view_display = 'core.entity_view_display.entity_test.entity_test.default';
+    $default_form_display = 'core.entity_view_display.entity_test.entity_test.default';
+    $manual_view_display = 'core.entity_view_display.entity_test.entity_test.manual';
+    $manual_form_display = 'core.entity_view_display.entity_test.entity_test.manual';
 
     // 1. Validate that "langcode" key is there.
-    $this->assertArrayHasKey('langcode', \Drupal::config($default_config_name)->get('hidden'));
+    $this->assertArrayHasKey('langcode', \Drupal::config($default_view_display)->get('hidden'));
+    $this->assertArrayHasKey('langcode', \Drupal::config($default_form_display)->get('hidden'));
+    $this->assertArrayHasKey('langcode', \Drupal::config($manual_view_display)->get('hidden'));
+    $this->assertArrayHasKey('langcode', \Drupal::config($manual_form_display)->get('hidden'));
 
     // 2. Uninstall language module.
     \Drupal::service('module_installer')->uninstall(['language']);
 
     // 3. Test that "langcode" key is removed from field config.
-    $this->assertArrayNotHasKey('langcode', \Drupal::config($default_config_name)->get('hidden'));
+    $this->assertArrayNotHasKey('langcode', \Drupal::config($default_view_display)->get('hidden'));
+    $this->assertArrayNotHasKey('langcode', \Drupal::config($default_form_display)->get('hidden'));
+    $this->assertArrayNotHasKey('langcode', \Drupal::config($manual_view_display)->get('hidden'));
+    $this->assertArrayNotHasKey('langcode', \Drupal::config($manual_form_display)->get('hidden'));
 
   }