diff --git a/UPGRADE-2.x.md b/UPGRADE-2.x.md
index 62247367..913040a8 100644
--- a/UPGRADE-2.x.md
+++ b/UPGRADE-2.x.md
@@ -1,2 +1,8 @@
 UPGRADE 2.x
 ===========
+
+### Tests
+
+All files under the ``Tests`` directory are now correctly handled as internal test classes. 
+You can't extend them anymore, because they are only loaded when running internal tests. 
+More information can be found in the [composer docs](https://getcomposer.org/doc/04-schema.md#autoload-dev).
diff --git a/composer.json b/composer.json
index 1fa8f213..b747ac1f 100644
--- a/composer.json
+++ b/composer.json
@@ -41,8 +41,14 @@
         "stof/doctrine-extensions-bundle": "<1.1 || >=2.0"
     },
     "autoload": {
-        "psr-4": { "Sonata\\TranslationBundle\\": "" }
+        "psr-4": { "Sonata\\TranslationBundle\\": "" },
+        "exclude-from-classmap": [
+            "Tests/"
+        ]
     },
+    "autoload-dev": {
+        "psr-4": { "Sonata\\TranslationBundle\\Tests\\": "Tests/" }
+     },
     "config": {
         "sort-packages": true
     },