diff --git a/core/tests/Drupal/Tests/Core/Asset/CssOptimizerUnitTest.php b/core/tests/Drupal/Tests/Core/Asset/CssOptimizerUnitTest.php
index 439d888..60384f0 100644
--- a/core/tests/Drupal/Tests/Core/Asset/CssOptimizerUnitTest.php
+++ b/core/tests/Drupal/Tests/Core/Asset/CssOptimizerUnitTest.php
@@ -201,6 +201,23 @@ function testOptimize($css_asset, $expected) {
   }
 
   /**
+   * Tests optimizing a CSS asset containing charset declaration.
+   */
+  function testOptimizeRemoveCharset() {
+    $css_asset = array(
+      'type' => 'inline',
+      'data' => '@charset "UTF-8";html{font-family:"sans-serif";}',
+      'preprocess' => FALSE,
+    );
+    $expected = 'html{font-family:"sans-serif";}';
+    $this->assertEquals(
+      $expected,
+      $this->optimizer->optimize($css_asset),
+      'CSS optimizing correctly removes the charset declaration.'
+    );
+  }
+
+  /**
    * Tests a file CSS asset with preprocessing disabled.
    */
   function testTypeFilePreprocessingDisabled() {