diff --git a/src/PIL/ImageShow.py b/src/PIL/ImageShow.py
index bb04c4e29c2..3368865a46d 100644
--- a/src/PIL/ImageShow.py
+++ b/src/PIL/ImageShow.py
@@ -227,6 +227,8 @@ def get_command_ex(self, file, title=None, **options):
 
 
 class IPythonViewer(Viewer):
+    """The viewer for IPython frontends."""
+
     def show_image(self, image, **options):
         ipython_display(image)
         return 1