diff --git a/src/main.nf b/src/main.nf
index cb1609ed772fe0765f7c7618e469bb8c72410e12..ea10ec887d3fa8a4caf2daaff6019baa1fa9e659 100644
--- a/src/main.nf
+++ b/src/main.nf
@@ -3,6 +3,7 @@ nextflow.enable.dsl=2
 /*
 Testing pipeline for marseq scRNASeq analysis
 */
+params.kmer_size = 31
 
 include { SPLIT } from "./modules/split"
 include { FASTKMERS } from "./modules/fastkmers"
diff --git a/src/modules/fastkmers.nf b/src/modules/fastkmers.nf
index c2b0028324fe79d8fa92ba47e64fac6d29f89b36..5a6ea264cdc42a6470c1980e3c97f06b86973365 100644
--- a/src/modules/fastkmers.nf
+++ b/src/modules/fastkmers.nf
@@ -15,7 +15,7 @@ process FASTKMERS {
     script:
     def args = task.ext.args ?: ''
     """
-    fastkmers -k 31 ${fastq} > ${fastq.simpleName}.csv
+    fastkmers -k ${params.kmer_size} ${fastq} > ${fastq.simpleName}.csv
 
 
     cat <<-END_VERSIONS > versions.yml