problem with balance labels in lme regression?

!qiime gneiss lme-regression \
    --p-formula "mouse_genotype * sample_type + timepoint" \
    --p-groups "cage_id" \
    --i-table IgA.deblur.balances.qza \
    --i-tree IgA.deblur.insertion-tree.named.qza \
    --m-metadata-file ../../data/IgA.map.txt \
    --o-visualization IgA.all.lme.mouse_genotype

Gives me the following error:

Plugin error from gneiss:

  numbers besides '0' and '1' are only allowed with **
      432L-d74aa370-dbeb-4162-bf79-133470bf4ad3 ~ mouse_genotype * sample_type + timepoint
                         ^^^^

Debug info has been saved to /tmp/qiime2-q2cli-err-_5zjbmey.log

biocore / gneiss

problem with balance labels in lme regression? #251