Passing velocyto samtools memory for sorting step

[wudustan]

I am running velocyto on slurm. I tried to pass samtools memory spec via

--samtools-memory 64G

and

--samtools-memory $((8*8042))

Both times I received an error.

Error: Invalid value for '--samtools-memory': '64G' is not a valid integer. samtools sort: couldn't allocate memory for bam_mem

How do I pass 64GB memory to samtools via the velocyto command line call?