samtool sort

my command :bowtie2 -x Guy11 -1 Guy11_FDSW210137750-1r_1.clean.fq.gz -2 Guy11_FDSW210137750-1r_2.clean.fq.gz | samtools sort -O bam -@ 5 -o Guy11.bam
and then it got error
sort: invalid option — ‘O’
open: No such file or directory
[bam_sort_core] fail to open file bam
Can people help me ?