diff --git a/lib/Twig/ExtensionSet.php b/lib/Twig/ExtensionSet.php
index a164296b6..a2b5d8391 100644
--- a/lib/Twig/ExtensionSet.php
+++ b/lib/Twig/ExtensionSet.php
@@ -469,3 +469,5 @@ final class Twig_ExtensionSet
         }
     }
 }
+
+class_alias('Twig_ExtensionSet', 'Twig\ExtensionSet', false);
diff --git a/lib/Twig/Filter.php b/lib/Twig/Filter.php
index 9b115ba56..e31076702 100644
--- a/lib/Twig/Filter.php
+++ b/lib/Twig/Filter.php
@@ -138,3 +138,5 @@ class Twig_Filter
 
 // For Twig 1.x compatibility
 class_alias('Twig_Filter', 'Twig_SimpleFilter', false);
+
+class_alias('Twig_Filter', 'Twig\TwigFilter', false);
diff --git a/lib/Twig/Function.php b/lib/Twig/Function.php
index 0e968e25f..22ab41541 100644
--- a/lib/Twig/Function.php
+++ b/lib/Twig/Function.php
@@ -128,3 +128,5 @@ class Twig_Function
 
 // For Twig 1.x compatibility
 class_alias('Twig_Function', 'Twig_SimpleFunction', false);
+
+class_alias('Twig_Function', 'Twig\TwigFunction', false);
diff --git a/lib/Twig/Test.php b/lib/Twig/Test.php
index a61417098..095b3da55 100644
--- a/lib/Twig/Test.php
+++ b/lib/Twig/Test.php
@@ -90,3 +90,5 @@ class Twig_Test
 
 // For Twig 1.x compatibility
 class_alias('Twig_Test', 'Twig_SimpleTest', false);
+
+class_alias('Twig_Test', 'Twig\TwigTest', false);
diff --git a/src/ExtensionSet.php b/src/ExtensionSet.php
new file mode 100644
index 000000000..e4a702e9a
--- /dev/null
+++ b/src/ExtensionSet.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace Twig;
+
+require __DIR__.'/../lib/Twig/ExtensionSet.php';
+
+if (\false) {
+    class ExtensionSet extends \Twig_ExtensionSet
+    {
+    }
+}