diff --git a/CHANGELOG.md b/CHANGELOG.md
index f35e4d78..3d0ab71a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,6 +31,7 @@ Thank you to everyone else that has contributed by reporting bugs, enhancements
 - [[PR #435](https://github.com/nf-core/viralrecon/pull/435)] - Changed to a patched cutadapt from nf-core modules, added `skip_noninternal_primers` param to allow users to process primers inside the pipeline, and added `threeprime_adapters` to determine whether primers are 3' or 5' adapters.
 - [[PR #446](https://github.com/nf-core/viralrecon/pull/446)] - Update nextclade & pangolin modules
 - [[PR #450](https://github.com/nf-core/viralrecon/pull/450)] - Patch nf schema - include integer & string as type for sample
+- [[PR #452](https://github.com/nf-core/viralrecon/pull/452)] - Fix `ch_blast_db` to have correct cardinality for blast/blastn
 
 ### Parameters
 
diff --git a/subworkflows/local/prepare_genome_illumina.nf b/subworkflows/local/prepare_genome_illumina.nf
index 997de413..591e2218 100644
--- a/subworkflows/local/prepare_genome_illumina.nf
+++ b/subworkflows/local/prepare_genome_illumina.nf
@@ -209,10 +209,12 @@ workflow PREPARE_GENOME {
                     UNTAR_BLAST_DB (
                         [ [:], params.blast_db ]
                     )
-                    ch_blast_db = UNTAR_BLAST_DB.out.untar.map { it[1] }
+                    ch_blast_db = UNTAR_BLAST_DB.out.untar
                     ch_versions = ch_versions.mix(UNTAR_BLAST_DB.out.versions)
                 } else {
-                    ch_blast_db = Channel.value(file(params.blast_db))
+                    ch_blast_db = Channel.value(
+                        [[id:'custom_blastdb'], file(params.blast_db)]
+                    )
                 }
             } else {
                 BLAST_MAKEBLASTDB (