Last round of adapting style of documenting argument default values.
diff --git a/Doc/library/xml.sax.reader.rst b/Doc/library/xml.sax.reader.rst
index 5d0b0dd..fb91389 100644
--- a/Doc/library/xml.sax.reader.rst
+++ b/Doc/library/xml.sax.reader.rst
@@ -1,4 +1,3 @@
-
:mod:`xml.sax.xmlreader` --- Interface for XML parsers
======================================================
@@ -48,7 +47,7 @@
methods may return ``None``.
-.. class:: InputSource([systemId])
+.. class:: InputSource(system_id=None)
Encapsulation of the information needed by the :class:`XMLReader` to read
entities.