Error in removeext(fastqFiles1) : could not find function "removeext"

Hi, 
:
I am trying to parse mouse haplotypes but I am confronted by this error:

library(harp)
> f <- file("*.fastq")
> ref1 <- "/path/to/C57BL_6NJ"
> ref2 <- "/path/to/CAST_EiJ"
> harp( f, index1prefix=ref1, index2prefix=ref2 )
Error in removeext(fastqFiles1) : could not find function "removeext"

any idea what i'm doing wrong? 

Thanks