diff --git a/core/tests/Drupal/Tests/Component/DrupalComponentTest.php b/core/tests/Drupal/Tests/Component/DrupalComponentTest.php
index 2924074..64dddb5 100644
--- a/core/tests/Drupal/Tests/Component/DrupalComponentTest.php
+++ b/core/tests/Drupal/Tests/Component/DrupalComponentTest.php
@@ -66,13 +66,15 @@ protected function findPhpClasses($dir) {
    *   The full path to the class that should be checked.
    */
   protected function assertNoCoreUsage($class_path) {
-    foreach (new \SplFileObject($class_path) as $line_number => $line) {
-      // Allow linking to Core files with @see docs. Its harmless and boosts DX
-      // because even outside projects can treat those links as examples.
-      if ($line && (strpos($line, '@see ') === FALSE)) {
-        $this->assertSame(FALSE, strpos($line, 'Drupal\\Core'), "Illegal reference to 'Drupal\\Core' namespace in $class_path at line $line_number");
+    $contents = file_get_contents($class_path);
+    if (preg_match_all('/^.*Drupal\\\Core.*$/m', $contents, $matches)) {
+      foreach ($matches[0] as $line) {
+        if ((strpos($line, '@see ') === FALSE)) {
+          $this->fail(
+            "Illegal reference to 'Drupal\\Core' namespace in $class_path"
+          );
+        }
       }
     }
   }
-
 }