Error in asMethod(object) : is an unknown item label error

I am doing association analysis using R.

This is the code I am using to generate rules:

rules <- apriori(trans, parameter = list(supp = .07,conf = 0.50,smax=6,minlen=3,maxlen=9,target = "rules"))

This code is giving me the set of rules for the given dataset, however if I try to find rules for particular consequent then I am getting an error.

Here is the code:

rules2 <- apriori(data=trans,parameter=list(supp = .07,conf = 0.5,smax=6,minlen=3,maxlen=9,target = "rules"), 
 appearance = list(default="lhs",rhs="CMDB"),
control = list(verbose=F)) 

and this is the error I am getting :

"Error in asMethod(object) : CMDB is an unknown item label"

How do I generate the correct rule?

Thanks.