diff --git a/modules/gatk4/haplotypecaller/main.nf b/modules/gatk4/haplotypecaller/main.nf
index 57f69ecd..2cd9e7d4 100644
--- a/modules/gatk4/haplotypecaller/main.nf
+++ b/modules/gatk4/haplotypecaller/main.nf
@@ -17,7 +17,7 @@ process GATK4_HAPLOTYPECALLER {
 
     output:
     tuple val(meta), path("*.vcf.gz"), emit: vcf
-    tuple val(meta), path("*.tbi")   , emit: tbi
+    tuple val(meta), path("*.tbi")   , optional:true, emit: tbi
     path "versions.yml"              , emit: versions
 
     when: