Reverse DNS lookup check not working

There seems to be a bug where DNS PTR (Reverse DNS lookup) checks do not
work in Xymon (4.3.7, but I don't recall seeing any fixes in the commits).
The man page for hosts.cfg says the format to use is:
 dns=TYPE:lookup
and one of the examples underneath for TYPE is PTR (reverse).  I have tried
this in small and capitals and neither work (the result is Name not found).
Using A does work though.
I wonder if it could be related to the fact that DiG needs to be invoked
with -x for PTR checks.  A quick look at the DiG man page suggests you could
use either:
# dig -t PTR my.ip.ad.dr.ess
Or:
# dig my.ip.ad.dr.ess PTR
However, this is not the case.  A closer looks reveals you have to use:
# dig -x my.ip.ad.dr.ess
So what I am saying is that the treatment for type PTR differs from the
other types, and that the parameters supplied to DiG (if Xymon uses DiG )
differ for PTR.
 
Tested manually with DiG 9.2.4 and the latest RHEL5:
9.3.6-P1-RedHat-9.3.6-20.P1.el5_8.6.

Kind regards, 

SebA