diff --git a/km3io/tools.py b/km3io/tools.py
index cf390d6118acc9dc90b1ffb422ed26e98d25d14e..0cf10f9370ea1ff6663b74ccb312348dafd3f0ce 100644
--- a/km3io/tools.py
+++ b/km3io/tools.py
@@ -107,6 +107,7 @@ class Branch:
         """Slicing magic"""
         if isinstance(item, str):
             return self.__getkey__(item)
+
         return self.__class__(self._tree,
                               self._mapper,
                               index_chain=self._index_chain + [item],