diff --git a/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
index d757647..b2e0507 100644
--- a/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
+++ b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
@@ -1141,7 +1141,7 @@ public function buildIdConflictForm(array &$form, FormStateInterface $form_state
     $form['warning'] = [
       '#type' => 'markup',
       '#markup' => '<h3>' . $this->t('Entities may be overwritten') . '</h3>' .
-        '<p>' . $this->t('Upgrades work on brand new sites, or sites with previously upgraded data. However, it looks like you have added other entities to your site, perhaps manually. These new entities <strong>may be overwritten</strong> if you run this upgrade.') . '</p>',
+        '<p>' . $this->t('Upgrades work on brand new sites, or sites with previously upgraded data. However, it looks like you have content in your site that is unknown to the migrate system; perhaps manually added. These new entities <strong>may be overwritten</strong> if you run this upgrade. For more information, see the online handbook entry for <a target="_blank" href=":id-conflicts-handbook">handling migration conflicts.</a>.', [':id-conflicts-handbook' => 'https://www.drupal.org/docs/8/upgrade/known-issues-when-upgrading-from-drupal-6-or-7-to-drupal-8#id_conflicts']) . '</p>',
     ];
 
     $items = [];
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeTestBase.php b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeTestBase.php
index 0117577..ce21f97 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeTestBase.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/MigrateUpgradeTestBase.php
@@ -37,7 +37,6 @@
     'telephone',
     'aggregator',
     'book',
-    'forum',
     'statistics',
   ];
 
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/d6/MigrateUpgradeConflicts6Test.php b/core/modules/migrate_drupal_ui/tests/src/Functional/d6/MigrateUpgradeConflicts6Test.php
index 7dfb3ec..3c73fff 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/d6/MigrateUpgradeConflicts6Test.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/d6/MigrateUpgradeConflicts6Test.php
@@ -15,11 +15,6 @@
 class MigrateUpgradeConflicts6Test extends MigrateUpgrade6Test {
 
   /**
-   * Use the Minimal profile to limit the number of modules enabled.
-   */
-  protected $profile = 'minimal';
-
-  /**
    * Modules to enable.
    *
    * @var array
@@ -27,7 +22,14 @@ class MigrateUpgradeConflicts6Test extends MigrateUpgrade6Test {
    * Forum module adds content, resulting in content id conflicts.
    */
   public static $modules = [
+    'language',
+    'content_translation',
+    'migrate_drupal_ui',
+    'telephone',
+    'aggregator',
+    'book',
     'forum',
+    'statistics',
   ];
 
   /**
diff --git a/core/modules/migrate_drupal_ui/tests/src/Functional/d7/MigrateUpgradeConflicts7Test.php b/core/modules/migrate_drupal_ui/tests/src/Functional/d7/MigrateUpgradeConflicts7Test.php
index cec3a53..22670a9 100644
--- a/core/modules/migrate_drupal_ui/tests/src/Functional/d7/MigrateUpgradeConflicts7Test.php
+++ b/core/modules/migrate_drupal_ui/tests/src/Functional/d7/MigrateUpgradeConflicts7Test.php
@@ -15,11 +15,6 @@
 class MigrateUpgradeConflicts7Test extends MigrateUpgrade7Test {
 
   /**
-   * Use the Minimal profile to limit the number of modules enabled.
-   */
-  protected $profile = 'minimal';
-
-  /**
    * Modules to enable.
    *
    * @var array
@@ -27,7 +22,14 @@ class MigrateUpgradeConflicts7Test extends MigrateUpgrade7Test {
    * Forum module adds content, resulting in content id conflicts.
    */
   public static $modules = [
+    'language',
+    'content_translation',
+    'migrate_drupal_ui',
+    'telephone',
+    'aggregator',
+    'book',
     'forum',
+    'statistics',
   ];
 
   /**