why cytosine_report output blank file?

[realzhang]

Dear dpryan79:
I use the command:
MethylDackel extract -@ 40 --cytosine_report --CHG --CHH --noCpG -o outFile genome.fa alignment.bam
and it output a blank file with size of 0.
If I remove the --noCpG in above, it works with output of all cytosines.
But if I only want the report of non-CpG cytosines?
Thank you very much.