diff --git a/src/main.nf b/src/main.nf
index d090293a8792128156fa741a77b01b7e05920999..9f55cb0555b54ea9747ddb49ddf017709a84a3f8 100644
--- a/src/main.nf
+++ b/src/main.nf
@@ -31,7 +31,7 @@ workflow {
   SUBSAMPLE_READ(fastq.r1.mix(fastq.r2))
   SPLIT(SUBSAMPLE_READ.out.fastq)
   FASTKMERS(SPLIT.out.fastq.transpose())
-  MERGEKMER(FASTKMERS.out.csv.map{it -> [[it[0].specie, it[0].sex], it[1]]}.groupTuple())
+  MERGEKMER(FASTKMERS.out.csv.map{it -> [['specie': it[0].specie, 'sex': it[0].sex], it[1]]}.groupTuple())
   COLLATEKMER(
     MERGEKMER.out.csv
       .filter{ it[0].sex == "male" }