diff --git a/ctapipe/core/container.py b/ctapipe/core/container.py
index b7d5e6b563a..43606921e36 100644
--- a/ctapipe/core/container.py
+++ b/ctapipe/core/container.py
@@ -174,7 +174,10 @@ def as_dict(self, recursive=False, flatten=False, add_prefix=False):
                     if flatten:
                         d.update({
                             "{}_{}".format(key, k): v
-                            for k, v in val.as_dict(recursive, add_prefix=add_prefix).items()
+                            for k, v in val.as_dict(
+                                recursive,
+                                add_prefix=add_prefix
+                            ).items()
                         })
                     else:
                         d[key] = val.as_dict(
@@ -232,8 +235,12 @@ def as_dict(self, recursive=False, flatten=False, add_prefix=False):
             for key, val in self.items():
                 if isinstance(val, Container) or isinstance(val, Map):
                     if flatten:
-                        d.update({"{}_{}".format(key, k): v
-                                  for k, v in val.as_dict(recursive, add_prefix=add_prefix).items()})
+                        d.update({
+                            "{}_{}".format(key, k): v
+                            for k, v in val.as_dict(
+                                recursive, add_prefix=add_prefix
+                            ).items()
+                        })
                     else:
                         d[key] = val.as_dict(
                             recursive=recursive,
diff --git a/ctapipe/io/tests/test_hdf5.py b/ctapipe/io/tests/test_hdf5.py
index a4644e7c5dc..24569c8666a 100644
--- a/ctapipe/io/tests/test_hdf5.py
+++ b/ctapipe/io/tests/test_hdf5.py
@@ -154,7 +154,7 @@ def test_writer_closes_file(temp_h5_file):
     with tempfile.NamedTemporaryFile() as f:
         with HDF5TableWriter(f.name, 'test') as h5_table:
 
-            assert h5_table._h5file.isopen  == 1
+            assert h5_table._h5file.isopen == 1
 
     assert h5_table._h5file.isopen == 0