diff --git a/ctapipe/io/obsconfig.py b/ctapipe/io/obsconfig.py
index a3dd91a7c4e..253908bedf8 100644
--- a/ctapipe/io/obsconfig.py
+++ b/ctapipe/io/obsconfig.py
@@ -29,7 +29,7 @@ def get_array_id_for_time( obstime ):
     return array_id, array_version
 
 
-class BaseConfig(object):
+class BaseConfig:
     pass
 
 
diff --git a/ctapipe/utils/fitshistogram.py b/ctapipe/utils/fitshistogram.py
index f3a34d34db5..fdc4efdad41 100644
--- a/ctapipe/utils/fitshistogram.py
+++ b/ctapipe/utils/fitshistogram.py
@@ -8,7 +8,7 @@
 __all__ = ['Histogram']
 
 
-class Histogram(object):
+class Histogram:
     """A simple N-dimensional histogram class that can be written or read
     from a FITS file. 
 
diff --git a/ctapipe/visualization/mpl.py b/ctapipe/visualization/mpl.py
index 0860e1a7ffe..32947483d91 100644
--- a/ctapipe/visualization/mpl.py
+++ b/ctapipe/visualization/mpl.py
@@ -14,9 +14,8 @@
 logger = logging.getLogger(__name__)
 
 
-class CameraDisplay(object):
-
-    """Camera Display using MatPlotLib
+class CameraDisplay:
+    """Camera Display using matplotlib.
 
     Parameters
     ----------
diff --git a/docs/development/code-guidelines.rst b/docs/development/code-guidelines.rst
index 63bead3c7ef..c8b3309d198 100644
--- a/docs/development/code-guidelines.rst
+++ b/docs/development/code-guidelines.rst
@@ -30,3 +30,6 @@ basic guidelines:
   added or removed, and the names are fixed.  Unlike C/C++ structs,
   namedtuples are _immutable_, meaning their data cannot be changed
   after they are constructed. 
+
+* Classes don't need to sub-class `object`, because we only support Python 3
+  and new-style classes are the default, i.e. subclassing `object` is superfluous.