diff --git a/prefixer/fix-twig.php b/prefixer/fix-twig.php
index c3737ffa99..97e8d51bab 100755
--- a/prefixer/fix-twig.php
+++ b/prefixer/fix-twig.php
@@ -243,7 +243,10 @@ foreach ($replacements as $singleFile) {
   file_put_contents($singleFile['file'], $data);
 }
 
-// Remove unwanted class aliases
+// Remove unwanted class aliases in lib/Twig subdirectories
+// We need to keep first level files in lib/Twig since most of them are still needed
+exec("find ../vendor-prefixed/twig/twig/lib/Twig -maxdepth 1 -mindepth 1 -type d -exec rm -rf '{}' \;");
+// Fix rest of the files in lib
 // Files in twig/lib directory contain class aliases which makes namespaced classes global
 // e.g. \class_alias('MailPoetVendor\\Twig_CompilerInterface', 'Twig_CompilerInterface', \false);
 $iterator = new RecursiveDirectoryIterator("../vendor-prefixed/twig/twig/lib", RecursiveDirectoryIterator::SKIP_DOTS);
diff --git a/tests/integration/Twig/FunctionsTest.php b/tests/integration/Twig/FunctionsTest.php
index 88b07d0f7c..6acc886565 100644
--- a/tests/integration/Twig/FunctionsTest.php
+++ b/tests/integration/Twig/FunctionsTest.php
@@ -9,7 +9,7 @@ use MailPoet\WP\Functions as WPFunctions;
 class FunctionsTest extends \MailPoetTest {
   public function testItExecutesIsRtlFunction() {
     $template = ['template' => '{% if is_rtl() %}rtl{% endif %}'];
-    $twig = new \MailPoetVendor\Twig_Environment(new \MailPoetVendor\Twig_Loader_Array($template));
+    $twig = new \MailPoetVendor\Twig_Environment(new \MailPoetVendor\Twig\Loader\ArrayLoader($template));
     WPFunctions::set(Stub::make(new WPFunctions, [
       'isRtl' => Stub::consecutive(true, false),
     ]));