diff --git a/Doc/library/urllib.error.rst b/Doc/library/urllib.error.rst
index 282329f..9c04859 100644
--- a/Doc/library/urllib.error.rst
+++ b/Doc/library/urllib.error.rst
@@ -39,6 +39,10 @@
       to a value found in the dictionary of codes as found in
       :attr:`http.server.BaseHTTPRequestHandler.responses`.
 
+   .. attribute:: reason
+
+      This is usually a string explaining the reason for this error.
+
 .. exception:: ContentTooShortError(msg, content)
 
    This exception is raised when the :func:`urlretrieve` function detects that