diff --git a/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php b/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php
index 84d025a..5cda7a9 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/ThemeInstallerTest.php
@@ -357,7 +357,7 @@ public function testThemeWithModuleDependency() {
     $this->assertTrue($this->moduleHandler()->moduleExists('test_module_required_by_theme'));
 
     $service = \Drupal::service('test_module_required_by_theme.service');
-    $this->assertInstanceOf(Service::class, $service);
+    $this->assertInstanceOf(\Drupal\test_module_required_by_theme\Service::class, $service);
   }
 
   /**