"Chapter" prefix with chapter title in docbook version 1.73.4 in PDF and HTML report

Hi,
 
I just upgraded my docbook version from 1.67.0 to version  1.74.3.
 
After upgrading I am getting "Chapter" prefix with Chapter title in TOC as well as in  report  for both PDF and HTML.

 
with 1.74.3 version I am getting chapter title as shown below.

Chapter 1. About this Document
 

with 1.67.0 version I was getting chapter title as shown below.
1. About this Document
 
I want the title as it was showing in version 1.67.0 without "Chapter" prefix. How can I change this title to look as older version 1.67.0? 

 
Thanks in advance.,
 
 Bela.