Error when running Project on plink files

[JMJOHNSON608]

When attempting to run project using plink files results in an Rcpp error:

fn <- gsub("\.bed", "",
system.file("extdata", "data_chr1.bed", package="flashpcaR"))
fn
f <- flashpca(fn, ndim=4,divisor="p",block_size=1000,do_loadings=TRUE,return_scale=TRUE,stand="binom2")
test<-project(fn,loadings=f$loadings,orig_mean=f$center,orig_sd=f$scale)

Which results in:

Error in project_plink_internal(X, loadings, ref_alleles, orig_mean, orig_sd, :
Expecting a string vector: [type=NULL; required=STRSXP].