diff --git a/src/nf_modules/Bowtie2/bowtie2.nf b/src/nf_modules/Bowtie2/bowtie2.nf
index 3a51b5c441cd3fab8e4d6011d3bf84c442a51fa9..d35c3442596cdc3e92faf55a121fb359e0cb8560 100644
--- a/src/nf_modules/Bowtie2/bowtie2.nf
+++ b/src/nf_modules/Bowtie2/bowtie2.nf
@@ -64,7 +64,7 @@ process mapping_fastq {
 
   input:
   set pair_id, file(reads) from fastq_files
-  file index from index_files.toList()
+  file index from index_files.collect()
 
   output:
   set pair_id, "*.bam" into bam_files
@@ -114,7 +114,7 @@ process mapping_fastq {
 
   input:
   file reads from fastq_files
-  file index from index_files.toList()
+  file index from index_files.collect()
 
   output:
   file "*.bam" into bam_files
diff --git a/src/nf_modules/Bowtie2/tests/mapping_paired.nf b/src/nf_modules/Bowtie2/tests/mapping_paired.nf
index 4cacca43e6a9dc45fbd9c4dde329d2499289f72d..7422b143606e720138d07ea3b04fe16d4301c117 100644
--- a/src/nf_modules/Bowtie2/tests/mapping_paired.nf
+++ b/src/nf_modules/Bowtie2/tests/mapping_paired.nf
@@ -20,7 +20,7 @@ process mapping_fastq {
 
   input:
   set pair_id, file(reads) from fastq_files
-  file index from index_files.toList()
+  file index from index_files.collect()
 
   output:
   set pair_id, "*.bam" into bam_files
diff --git a/src/nf_modules/Bowtie2/tests/mapping_single.nf b/src/nf_modules/Bowtie2/tests/mapping_single.nf
index 19f491af7dab4092f8e9997561b0c4f8824d7293..5f6a9de9d88eba6151af957fc07433129b9ae196 100644
--- a/src/nf_modules/Bowtie2/tests/mapping_single.nf
+++ b/src/nf_modules/Bowtie2/tests/mapping_single.nf
@@ -19,7 +19,7 @@ process mapping_fastq {
 
   input:
   file reads from fastq_files
-  file index from index_files.toList()
+  file index from index_files.collect()
 
   output:
   file "*.bam" into bam_files