diff --git a/km3io/offline.py b/km3io/offline.py
index 82cf5f47b03194c27d0cbbcfc699653754a89f1f..14043bc88432082b4e7dcf3dfe741ae71e617f96 100644
--- a/km3io/offline.py
+++ b/km3io/offline.py
@@ -151,7 +151,9 @@ class Usr:
 
     def __getitem_flat__(self, item):
         if self._index_chain:
-            return _unfold_indices(self._usr_data, self._index_chain)[:, self._usr_idx_lookup[item]]
+            return _unfold_indices(
+                self._usr_data, self._index_chain)[:,
+                                                   self._usr_idx_lookup[item]]
         else:
             return self._usr_data[:, self._usr_idx_lookup[item]]
 
@@ -197,8 +199,8 @@ class OfflineReader:
     def events(self):
         """The `E` branch, containing all offline events."""
         return OfflineBranch(self._tree,
-                      mapper=EVENTS_MAP,
-                      subbranchmaps=SUBBRANCH_MAPS)
+                             mapper=EVENTS_MAP,
+                             subbranchmaps=SUBBRANCH_MAPS)
 
     @cached_property
     def header(self):
diff --git a/km3io/tools.py b/km3io/tools.py
index c44af93de281861cdf5a6f532225225f0959d496..6775e1ee8ebc24e44191196e113ab1478fe467fd 100644
--- a/km3io/tools.py
+++ b/km3io/tools.py
@@ -26,9 +26,10 @@ def _unfold_indices(obj, indices):
         try:
             obj = obj[idx]
         except IndexError:
-            print("IndexError while accessing an item from '{}' at depth {} ({}) "
-                  "using the index chain {}"
-                  .format(repr(original_obj), depth, idx, indices))
+            print(
+                "IndexError while accessing an item from '{}' at depth {} ({}) "
+                "using the index chain {}".format(repr(original_obj), depth,
+                                                  idx, indices))
             raise
     return obj
 
@@ -62,7 +63,7 @@ class Branch:
         if subbranchmaps is not None:
             for mapper in subbranchmaps:
                 subbranch = self.__class__(self._tree,
-                                   mapper=mapper,
+                                           mapper=mapper,
                                            index_chain=self._index_chain)
                 self._subbranches.append(subbranch)
         for subbranch in self._subbranches:
@@ -129,8 +130,10 @@ class Branch:
         elif isinstance(self._index_chain[-1], int):
             return 1
         else:
-            return len(_unfold_indices(self._branch[self._keymap['id']].lazyarray(
-                basketcache=BASKET_CACHE), self._index_chain))
+            return len(
+                _unfold_indices(
+                    self._branch[self._keymap['id']].lazyarray(
+                        basketcache=BASKET_CACHE), self._index_chain))
 
     def __str__(self):
         return "Number of elements: {}".format(len(self._branch))
diff --git a/tests/test_offline.py b/tests/test_offline.py
index ef5c798dd754181915729b8ece8e42412fe60127..4f47a4917e3cd77104dfaed1f4f2ebc058702cc1 100644
--- a/tests/test_offline.py
+++ b/tests/test_offline.py
@@ -154,7 +154,8 @@ class TestOfflineEvents(unittest.TestCase):
 
     def test_index_chaining(self):
         assert np.allclose(self.events[3:5].n_hits, self.events.n_hits[3:5])
-        assert np.allclose(self.events[3:5][0].n_hits, self.events.n_hits[3:5][0])
+        assert np.allclose(self.events[3:5][0].n_hits,
+                           self.events.n_hits[3:5][0])
 
     def test_str(self):
         assert str(self.n_events) in str(self.events)
@@ -344,7 +345,6 @@ class TestUsr(unittest.TestCase):
             self.f.events.usr.DeltaPosZ)
 
 
-
 class TestNestedMapper(unittest.TestCase):
     def test_nested_mapper(self):
         self.assertEqual('pos_x', _nested_mapper("trks.pos.x"))
diff --git a/tests/test_tools.py b/tests/test_tools.py
index 3c4b6559e0158af6414111b94ca3cce717f2b6bb..857f9c84a7939f0676560afc29cb74bc41d0c85a 100644
--- a/tests/test_tools.py
+++ b/tests/test_tools.py
@@ -30,7 +30,8 @@ class TestUnfoldIndices(unittest.TestCase):
         assert data[indices[0]][indices[1]] == _unfold_indices(data, indices)
 
         indices = [slice(1, 9, 2), slice(1, 4), 2]
-        assert data[indices[0]][indices[1]][indices[2]] == _unfold_indices(data, indices)
+        assert data[indices[0]][indices[1]][indices[2]] == _unfold_indices(
+            data, indices)
 
     def test_unfold_indices_raises_index_error(self):
         data = range(10)