correct "sources" file for debugging?

Hi Experts:

I have a short "sources" file below which seems not generating correct debug
info: driver (testva.sys) size of the debug version is only a bit bigger
than fee build and could not set break point in WinDbg. Could you see
anything incorrect here? What is misssing to generate full debug info?

Thanks in Advance!
Polaris

---------- Sources -------------
TARGETNAME=testva
TARGETTYPE=DRIVER
TARGETPATH=obj

MSC_OPTIMIZATION=/Od

TARGETLIBS= $(DDK_LIB_PATH)\ndis.lib

NTDEBUG=ntsd
NTDEBUGTYPE=windbg

C_DEFINES=$(C_DEFINES) -DNDIS_MINIPORT_DRIVER=1
C_DEFINES=$(C_DEFINES) -DNDIS_WDM=1 -DWINNT -DWIN2000 $(DEBFLAGS)
C_DEFINES=$(C_DEFINES) -DNDIS50_MINIPORT=1

INCLUDES=$(DDK_INC_PATH);

..asm{$O\}.obj: ml /coff /Fo$@ /c $<

SOURCES= testva.c oid.c hExcept3.asm testva.rc