Racon error: empty overlap set!

[lacassee]

Hi, I am try to run Racon on nanopore sequenced and porechop trimmed data (1580.fq.gz) with my reference genome (1580.fa) and my minimap2 alignement (1580.bam).
minimap2 alignement was genereted with this commande :
minimap2 -a ./ref_genome/1580.fa ./3-trimmed_file/1580.fq.gz -o ./5-alignement/1580.sam

Here is my unsuccessful Racon command :
racon -t 4 -m 8 -x -6 -g -8 -w 500 ../ref_genome/1580.fa ../5-alignement/1580.sam ../3-trimmed_file/1580.fq.gz

Thank you very much.