AC,AF, and AN INFO fields are not defined in output from HaplotypeCaller

Hi,

I have a problem where the output vcf from the haplotypecaller doesn't include meta-information lines for the AC,AF, and AN info fields, yet one of the records in the vcf contains these info fields.

$ grep -e "##INFO=<ID=AC" NA12878-I9_16_chr6.variant.vcf
$ grep -e "AC=2;" NA12878-I9_16_chr6.variant.vcf
chr6    15613333    rs145086187    TGC    AGT    331.78    PASS    AC=2;AF=1.00;AN=2    GT:GQ    1/1:24

How can I get the haplotypecaller to add the meta-information lines for these info fields?

Thanks,
David