diff --git a/km3io/tools.py b/km3io/tools.py
index d36748de25433b707dce0c02b81983b1bb84dd72..31ffb0639090e48ab47ff6a41704bd96ee2a7fd5 100644
--- a/km3io/tools.py
+++ b/km3io/tools.py
@@ -6,6 +6,7 @@ import uproot
 BASKET_CACHE_SIZE = 110 * 1024**2
 BASKET_CACHE = uproot.cache.ThreadSafeArrayCache(BASKET_CACHE_SIZE)
 
+
 class cached_property:
     """A simple cache decorator for properties."""
     def __init__(self, function):
@@ -56,8 +57,8 @@ class Branch:
     def _initialise_keys(self):
         """Create the keymap and instance attributes for branch keys"""
         # TODO: this could be a cached property
-        keys = set(k.decode('utf-8') for k in self._branch.keys()) - set(
-            self._mapper.exclude)
+        keys = set(k.decode('utf-8')
+                   for k in self._branch.keys()) - set(self._mapper.exclude)
         self._keymap = {
             **{self._mapper.attrparser(k): k
                for k in keys},
@@ -132,6 +133,7 @@ class Branch:
                                                self._mapper.name, length,
                                                's' if length > 1 else '')
 
+
 class Usr:
     """Helper class to access AAObject `usr` stuff"""
     def __init__(self, mapper, branch, index=None):
@@ -165,7 +167,8 @@ class Usr:
         # to massively increase the performance. This needs triple check if
         # it's always the case.
         self._usr_names = [
-            n.decode("utf-8") for n in self._branch[self._usr_key + '_names'].lazyarray(
+            n.decode("utf-8")
+            for n in self._branch[self._usr_key + '_names'].lazyarray(
                 basketcache=BASKET_CACHE)[0]
         ]
         self._usr_idx_lookup = {
@@ -207,12 +210,12 @@ class Usr:
 
     def __getitem_nested__(self, item):
         data = self._branch[self._usr_key + '_names'].lazyarray(
-                # TODO this will be fixed soon in uproot,
-                # see https://github.com/scikit-hep/uproot/issues/465
-                uproot.asgenobj(
-                    uproot.SimpleArray(uproot.STLVector(uproot.STLString())),
-                    self._branch[self._usr_key + '_names']._context, 6),
-                basketcache=BASKET_CACHE)
+            # TODO this will be fixed soon in uproot,
+            # see https://github.com/scikit-hep/uproot/issues/465
+            uproot.asgenobj(
+                uproot.SimpleArray(uproot.STLVector(uproot.STLString())),
+                self._branch[self._usr_key + '_names']._context, 6),
+            basketcache=BASKET_CACHE)
         if self._index is None:
             return data
         else:
diff --git a/tests/test_tools.py b/tests/test_tools.py
index 4506869935a5a7f1331560744a6fb79c06e6e37f..bceb4a0b45fb77784274513b337d83e79c7de303 100644
--- a/tests/test_tools.py
+++ b/tests/test_tools.py
@@ -3,6 +3,7 @@
 import unittest
 from km3io.tools import _to_num, cached_property
 
+
 class TestToNum(unittest.TestCase):
     def test_to_num(self):
         self.assertEqual(10, _to_num("10"))