diff --git a/core/tests/Drupal/Tests/Core/Config/ConfigTest.php b/core/tests/Drupal/Tests/Core/Config/ConfigTest.php
index 2cfc1b32014..0fba72d8fc1 100644
--- a/core/tests/Drupal/Tests/Core/Config/ConfigTest.php
+++ b/core/tests/Drupal/Tests/Core/Config/ConfigTest.php
@@ -7,7 +7,6 @@ use Drupal\Core\Render\Markup;
 use Drupal\Tests\UnitTestCase;
 use Drupal\Core\Config\Config;
 use Drupal\Core\Config\ConfigValueException;
-use PHPUnit\Framework\Error\Warning;
 
 /**
  * Tests the Config.
@@ -270,7 +269,12 @@ class ConfigTest extends UnitTestCase {
     $this->config->set('testData', 1);
 
     // Attempt to treat the single value as a nested item.
-    $this->expectException(PHP_VERSION_ID >= 80000 ? \Error::class : Warning::class);
+    if (PHP_VERSION_ID >= 80000) {
+      $this->expectError();
+    }
+    else {
+      $this->expectWarning();
+    }
     $this->config->set('testData.illegalOffset', 1);
   }