core/modules/system/src/Tests/Theme/TwigExtensionTest.php             | 4 ++--
 .../modules/twig_extension_test/twig_extension_test.services.yml      | 2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/core/modules/system/src/Tests/Theme/TwigExtensionTest.php b/core/modules/system/src/Tests/Theme/TwigExtensionTest.php
index 6b960b0..d195200 100644
--- a/core/modules/system/src/Tests/Theme/TwigExtensionTest.php
+++ b/core/modules/system/src/Tests/Theme/TwigExtensionTest.php
@@ -35,7 +35,7 @@ function testTwigExtensionLoaded() {
   /**
    * Tests that the Twig extension's filter produces expected output.
    */
-  function DISABLEDtestTwigExtensionFilter() {
+  function testTwigExtensionFilter() {
     $this->config('system.theme')
       ->set('default', 'test_theme')
       ->save();
@@ -49,7 +49,7 @@ function DISABLEDtestTwigExtensionFilter() {
   /**
    * Tests that the Twig extension's function produces expected output.
    */
-  function DISABLEDtestsTwigExtensionFunction() {
+  function testsTwigExtensionFunction() {
     $this->config('system.theme')
       ->set('default', 'test_theme')
       ->save();
diff --git a/core/modules/system/tests/modules/twig_extension_test/twig_extension_test.services.yml b/core/modules/system/tests/modules/twig_extension_test/twig_extension_test.services.yml
index 491d1e8..dea3cac 100644
--- a/core/modules/system/tests/modules/twig_extension_test/twig_extension_test.services.yml
+++ b/core/modules/system/tests/modules/twig_extension_test/twig_extension_test.services.yml
@@ -2,5 +2,7 @@ services:
   twig_extension_test.twig.test_extension:
     arguments: ['@renderer']
     class: Drupal\twig_extension_test\TwigExtension\TestExtension
+    calls:
+      - [setThemeRegistry, ['@theme.registry']]
     tags:
       - { name: twig.extension }