Tweak key conversion

src/Jenssegers/Mongodb/Model.php

@@ -207,13 +207,12 @@ abstract class Model extends \Jenssegers\Eloquent\Model {
         // Convert _id to MongoId.
         if ($key == '_id' and is_string($value))
         {
-            $this->attributes[$key] = new MongoId($value);
+            $builder = $this->newBaseQueryBuilder();
+            $value = $builder->convertKey($value);
         }
-        else
-        {
+
         parent::setAttribute($key, $value);
     }
-    }
 
     /**
      * Convert the model's attributes to an array.