diff --git a/linkchecker.install b/linkchecker.install
index 65c1a631cb4d1c1ab8f07d0f56903677b60f5112..1111bf47bf682692b8b0586f96d8e6e3a29b4ec1 100644
--- a/linkchecker.install
+++ b/linkchecker.install
@@ -31,7 +31,8 @@ function linkchecker_schema() {
     'description' => 'Stores entities from which links where extracted.',
     'fields' => [
       'entity_id' => [
-        'type' => 'int',
+        'type' => 'varchar',
+        'length' => 128,
         'not null' => TRUE,
         'description' => 'Entity ID.',
       ],
@@ -218,3 +219,25 @@ function linkchecker_update_8007(&$sandbox) {
     return t('The entity_id field storage definition successfully uninstalled.');
   }
 }
+
+/**
+ * Change entity_id column to varchar to support string entity IDs.
+ */
+function linkchecker_update_8008() {
+  $database = \Drupal::database();
+  $schema = $database->schema();
+
+  // Drop the primary key first.
+  $schema->dropPrimaryKey('linkchecker_index');
+
+  // Change the column type from int to varchar.
+  $schema->changeField('linkchecker_index', 'entity_id', 'entity_id', [
+    'type' => 'varchar',
+    'length' => 128,
+    'not null' => TRUE,
+    'description' => 'Entity ID.',
+  ]);
+
+  // Recreate the primary key.
+  $schema->addPrimaryKey('linkchecker_index', ['entity_id', 'entity_type']);
+}
diff --git a/tests/src/Kernel/LinkcheckerUpdateTest.php b/tests/src/Kernel/LinkcheckerUpdateTest.php
new file mode 100644
index 0000000000000000000000000000000000000000..b3707533b1e7461bbaee74f55a43ee10b4e47193
--- /dev/null
+++ b/tests/src/Kernel/LinkcheckerUpdateTest.php
@@ -0,0 +1,110 @@
+<?php
+
+namespace Drupal\Tests\linkchecker\Kernel;
+
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests for linkchecker update hooks.
+ *
+ * @group linkchecker
+ */
+class LinkcheckerUpdateTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'system',
+    'linkchecker',
+    'user',
+  ];
+
+  /**
+   * The database connection.
+   *
+   * @var \Drupal\Core\Database\Connection
+   */
+  protected $database;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp(): void {
+    parent::setUp();
+    $this->installSchema('linkchecker', 'linkchecker_index');
+    $this->database = $this->container->get('database');
+  }
+
+  /**
+   * Tests linkchecker_update_8008 converts entity_id column to varchar.
+   *
+   * @covers ::linkchecker_update_8008
+   */
+  public function testUpdate8008EntityIdColumnTypeChange(): void {
+    $schema = $this->database->schema();
+
+    // Revert the schema to the old state with int entity_id column.
+    $schema->dropPrimaryKey('linkchecker_index');
+    $schema->changeField('linkchecker_index', 'entity_id', 'entity_id', [
+      'type' => 'int',
+      'not null' => TRUE,
+      'description' => 'Entity ID.',
+    ]);
+    $schema->addPrimaryKey('linkchecker_index', ['entity_id', 'entity_type']);
+
+    // Insert some test data with integer entity IDs.
+    $this->database->insert('linkchecker_index')
+      ->fields([
+        'entity_id' => 123,
+        'entity_type' => 'node',
+        'last_extracted_time' => 1234567890,
+      ])
+      ->execute();
+
+    $this->database->insert('linkchecker_index')
+      ->fields([
+        'entity_id' => 456,
+        'entity_type' => 'paragraph',
+        'last_extracted_time' => 1234567891,
+      ])
+      ->execute();
+
+    // Run the update function.
+    $module_path = \Drupal::service('extension.path.resolver')->getPath('module', 'linkchecker');
+    require_once $module_path . '/linkchecker.install';
+    linkchecker_update_8008();
+
+    // Verify the data is still intact.
+    $results = $this->database->select('linkchecker_index', 'li')
+      ->fields('li')
+      ->orderBy('entity_id')
+      ->execute()
+      ->fetchAll();
+
+    $this->assertCount(2, $results);
+    $this->assertEquals('123', $results[0]->entity_id);
+    $this->assertEquals('node', $results[0]->entity_type);
+    $this->assertEquals('456', $results[1]->entity_id);
+    $this->assertEquals('paragraph', $results[1]->entity_type);
+
+    // Verify that we can now insert string entity IDs.
+    $this->database->insert('linkchecker_index')
+      ->fields([
+        'entity_id' => 'string-entity-id-789',
+        'entity_type' => 'custom_entity',
+        'last_extracted_time' => 1234567892,
+      ])
+      ->execute();
+
+    $result = $this->database->select('linkchecker_index', 'li')
+      ->fields('li')
+      ->condition('entity_id', 'string-entity-id-789')
+      ->execute()
+      ->fetchObject();
+
+    $this->assertEquals('string-entity-id-789', $result->entity_id);
+    $this->assertEquals('custom_entity', $result->entity_type);
+  }
+
+}