Linux Ethernet Bridging - Feb 2012 - [Bridge] Strange STP hello timing problem

Have 3 bridges in serie:

A - B - C
A is designated root.

In B I can see with tcpdump that I receive STP Hellos ever 2 secs from A, this
is normal.
However B forwards hellos to C every 20 secs( max age timer). This makes topo
calculation
go into spin every now and then. Should not B forward hellos as they come from
A(every 2 secs)?

 Jocke