[galaxy-user] Help with sam to bam

Hi, I was wondering if someone could help me with an error message I'm getting after performing a sam to bam conversion in galaxy. I've used Bowtie to map sequence reads to a custom fasta file corresponding to one chromosome in my organism. The mapping seems to work fine, but when I attempt a sam to bam conversion, I receive the folowing error message: An error occurred running this job: Samtools Version: 0.1.12 (r862) Error creating indexes from reference (/galaxy/main_database/files/002/977/dataset_2977193.dat), [fai_build_core] line length exceeds 65535 in sequence 'LGVII'. Segmentation fault Any help would be appreciated. Thanks, Zack