DOCBOOK: substeps are not numbering

Hi,

I have defined procedure which has steps and substeps however substeps
are coming as

a
b
c
d

where as the explanation at http://docbook.org/tdg/en/html/substeps.html
says 
"
Processing expectations

Formatted as a displayed block. SubSteps are almost always numbered.
"

I am using docbook V4.1 with dsssl 1.72 is this something I can refigure
somewhere or ?

TIA. 
-- 
Togan Muftuoglu