CDEF broke in Ubuntu Xenial

I have a collection of system graphs which broke upon upgrading our 
management server to Ubuntu Xenial.    I have Googled various "the 
parser in rrdtool 1.5 is much stricter", etc, but nothing that actually 
gives me a good idea the exact source of the problem.   Can anyone see 
an obvious problem with the CDEF below?   Thanks.

CDEF:snmp-net-in=TIME,1462826104,GT,snmp-net-in1,snmp-net-in1,UN,0,snmp-net-in1,IF,IF

ERROR: don't understand 
'snmp-net-out1,snmp-net-out1,UN,0,snmp-net-out1,IF,IF'


Mat