diff --git a/libs/Daux.php b/libs/Daux.php
index 5d480e6..11a0c19 100644
--- a/libs/Daux.php
+++ b/libs/Daux.php
@@ -306,7 +306,9 @@ class Daux
             throw new \RuntimeException("Class '$class' not found. We cannot use it as a Processor");
         }
 
-        //TODO :: check that it implements processor
+        if (!array_key_exists("Todaymade\\Daux\\Processor", class_parents($class))) {
+            throw new \RuntimeException("Class '$class' invalid, should extend '\\Todaymade\\Daux\\Processor'");
+        }
 
         return $class;
     }
diff --git a/libs/Tree/Content.php b/libs/Tree/Content.php
index 5d29f51..77e910e 100644
--- a/libs/Tree/Content.php
+++ b/libs/Tree/Content.php
@@ -72,6 +72,10 @@ class Content extends Entry
 
     public function isIndex()
     {
+        // At some point, it was recommended that
+        // an index page starts with an underscore.
+        // This is not mandatory anymore, both with
+        // and without underscore are supported.
         return $this->name == 'index' || $this->name == '_index';
     }