InVEx failure on power file creation from wiggle

My first attempt to use InVEx has hit a roadblock at the wiggle-processing step. Here's the format of the wiggle file (test.wiggle) and of the reference FASTA:

track type=wiggle_0 name=SomaticCoverage
fixedStep chrom=1 start=30366 step=1

>1 CM000663.1 Homo sapiens chromosome 1, GRCh37 primary reference assembly

And here's the error:

Traceback (most recent call last):
File "[codepath]/invex/InVEx-1.0.1/invex/", line 124, in
File "[codepath]/invex/InVEx-1.0.1/invex/", line 101, in createNtPowerFileFromWig
power.create_nt_power_file_from_wig(ref, inputWigPath, outputPowerFilename)
File "[codepath]/invex/InVEx-1.0.1/invex/library/", line 37, in create_nt_power_file_from_wig
encodedChromosome = [chr(self.asciiEncoding[0])] * len(referenceObj.genome[key][:])
File "[codepath]/invex/pyfasta-0.5.1/pyfasta/", line 112, in __getitem__
c = self.index[i]
KeyError: 'chr1'

My first thought would be a mismatch in contig naming, but neither my reference nor my wiggle use the "chr1" format; they're all bare chromosome numbers. I've tried on several wiggle files, named either .wig or .wiggle. I glanced at the appropriate lines in the code, but I'm not immediately familiar with what pyfasta does. Can anyone tell me what's going wrong? Thanks!

chromosome format

Check out the code... I have not looked, but perhaps it is expecting chromosomes to be formatted like 'chr1' rather than '1'.