Memory Issues when running tajima module

Hi

I am running vcf-kit (version 0.2.6) from a anaconda installation. I am trying to run the tajima module using the following command:
`vk tajima 10000 10000 chromosme.vcf.gz > chromosome_td.tsv`

Each time I run the command, it runs for a few minutes but quickly consumes a lot of RAM before quitting. Curious if you know how to prevent this? 

Thanks!

