Can't run mop using fiss

I'm getting the following memoryview error, seems like there is a bug here?:

fissfc mop -w DNA_RNA_Mutation_Lung -p vanallen-firecloud-dfci
WARNING: Delete 1138 files in gs://fc-be4ff012-c791-409b-a489-c78979f55422 (DNA_RNA_Mutation_Lung)
Are you sure? [y/yes (default: no)]: yes
TypeError: memoryview: a bytes-like object is required, not 'str'