diff --git a/sigal/gallery.py b/sigal/gallery.py
index 831b163..08a8bbf 100644
--- a/sigal/gallery.py
+++ b/sigal/gallery.py
@@ -38,7 +38,7 @@ from .writer import Writer
 DESCRIPTION_FILE = "index.md"
 
 
-class Gallery:
+class Gallery(object):
     "Prepare images"
 
     def __init__(self, settings, input_dir, output_dir, force=False,
diff --git a/sigal/image.py b/sigal/image.py
index 4039f64..7476e89 100644
--- a/sigal/image.py
+++ b/sigal/image.py
@@ -37,7 +37,7 @@ from PIL import ImageDraw, ImageOps, ImageFile
 EXIF_ORIENTATION_TAG = 274
 
 
-class Image:
+class Image(object):
     """ Image container
 
     resize, thumbnail, ...
diff --git a/sigal/writer.py b/sigal/writer.py
index 63e2fd7..e93e989 100644
--- a/sigal/writer.py
+++ b/sigal/writer.py
@@ -54,7 +54,7 @@ def link(url, title):
     return '<a href="%s">%s</a>' % (url, title)
 
 
-class Writer():
+class Writer(object):
     """Generate html pages for each directory of images."""
 
     def __init__(self, settings, output_dir, theme=None):