bpo-42843: Keep Sphinx 1.8 and Sphinx 2 compatibility (GH-24282)
diff --git a/Doc/library/base64.rst b/Doc/library/base64.rst
index 25b3a4c..2f24bb6 100644
--- a/Doc/library/base64.rst
+++ b/Doc/library/base64.rst
@@ -199,7 +199,7 @@
.. versionadded:: 3.4
-.. function:: a85decode(b, *, foldspaces=False, adobe=False, ignorechars=b' \t\n\r\v')
+.. function:: a85decode(b, *, foldspaces=False, adobe=False, ignorechars=b' \\t\\n\\r\\v')
Decode the Ascii85 encoded :term:`bytes-like object` or ASCII string *b* and
return the decoded :class:`bytes`.