diff --git a/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php b/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
index 0e7ac2f..2c9a015 100644
--- a/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
@@ -121,7 +121,7 @@ protected function setUp() {
     $logger = $this->getMock('Psr\Log\LoggerInterface');
     $this->themeHandler = new TestThemeHandler($this->root, $this->configFactory, $this->moduleHandler, $this->state, $this->infoParser, $logger, $this->cssCollectionOptimizer, $this->configInstaller, $this->configManager, $this->routeBuilderIndicator, $this->extensionDiscovery);
 
-    $cache_tags.invalidator = $this->getMock('Drupal\Core\Cache\CacheTagsInvalidatorInterface');
+    $cache_tags_invalidator = $this->getMock('Drupal\Core\Cache\CacheTagsInvalidatorInterface');
     $this->getContainerWithCacheTagsInvalidator($cache_tags_invalidator);
   }