diff --git a/docs/handbook/writing-your-own-file-decoder.rst b/docs/handbook/writing-your-own-file-decoder.rst
index 410bf4e7b..49b882c71 100644
--- a/docs/handbook/writing-your-own-file-decoder.rst
+++ b/docs/handbook/writing-your-own-file-decoder.rst
@@ -105,7 +105,9 @@ Note that the image plugin must be explicitly registered using
 :py:func:`PIL.Image.register_open`. Although not required, it is also a good
 idea to register any extensions used by this format.
 
-Once the plugin has been imported, it can be used::
+Once the plugin has been imported, it can be used:
+
+.. code-block:: python
 
     from PIL import Image
     import SpamImagePlugin
@@ -423,4 +425,3 @@ Python-based file decoder:
 
 3. Cleanup: The decoder instance's ``cleanup`` method is called.
 
-