diff --git a/core/modules/locale/tests/src/Functional/LocaleLocaleLookupTest.php b/core/modules/locale/tests/src/Functional/LocaleLocaleLookupTest.php
index 27bae5e2da..0938895083 100644
--- a/core/modules/locale/tests/src/Functional/LocaleLocaleLookupTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleLocaleLookupTest.php
@@ -2,9 +2,9 @@
 
 namespace Drupal\Tests\locale\Functional;
 
+use Drupal\Core\StringTranslation\PluralTranslatableMarkup;
 use Drupal\language\Entity\ConfigurableLanguage;
 use Drupal\Tests\BrowserTestBase;
-use Drupal\Tests\Core\Cache\CacheCollectorHelper;
 
 /**
  * Tests LocaleLookup.
@@ -56,4 +56,46 @@ public function testLanguageFallbackDefaults() {
     $this->assertEqual($context['operation'], 'locale_lookup');
   }
 
+  /**
+   * Test old plural style @count[number] fix.
+   *
+   * @dataProvider providerTestFixOldPluralStyle
+   */
+  public function testFixOldPluralStyle($translation_value, $expected) {
+    /** @var \Drupal\locale\StringDatabaseStorage $string_storage */
+    $string_storage = \Drupal::service('locale.storage');
+
+    $string = $string_storage->findString(['source' => 'Member for', 'context' => '']);
+
+    // Create translation with old @count[2] plural style.
+    $string_storage->createTranslation([
+      'lid' => $string->getId(),
+      'language' => 'fr',
+      'translation' => $translation_value,
+    ])->save();
+
+    drupal_flush_all_caches();
+    $this->drupalGet('');
+    $this->assertSession()->pageTextContains($expected);
+
+    // Assert that source not changed.
+    $translation = $string_storage->findTranslation(['language' => 'fr', 'lid' => $string->getId()])->translation;
+    $this->assertSame($translation_value, $translation);
+  }
+
+  /**
+   * Provides data for testFixOldPluralStyle().
+   *
+   * @return array
+   *   An array of test data:
+   *     - translation value
+   *     - expected result
+   */
+  public function providerTestFixOldPluralStyle() {
+    return [
+      'non-plural translation' => ['@count[2] non-plural test', '@count[2] non-plural test'],
+      'plural translation' => ['@count[2] plural test' . PluralTranslatableMarkup::DELIMITER, '@count plural test'],
+    ];
+  }
+
 }