diff --git a/core/modules/system/src/Tests/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php b/core/modules/system/src/Tests/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
index 18b5f69..7cdd875 100644
--- a/core/modules/system/src/Tests/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
+++ b/core/modules/system/src/Tests/Asset/ResolvedLibraryDefinitionsFilesMatchTest.php
@@ -100,6 +100,7 @@ public function setUp() {
     $this->libraryDiscovery = $this->container->get('library.discovery');
 
     // Install all core themes.
+    sort($this->allThemes);
     $this->container->get('theme_installer')->install($this->allThemes);
 
     // Enable all core modules.
@@ -182,7 +183,6 @@ protected function getAllLibraries() {
     $extensions += $themes;
     $theme_list = array_keys($themes);
     sort($theme_list);
-    sort($this->allThemes);
     $this->assertEqual($this->allThemes, $theme_list, 'All core themes are installed.');
 
     $libraries['core'] = $this->libraryDiscovery->getLibrariesByExtension('core');