diff --git a/R/variant_classifier.R b/R/variant_classifier.R
index 29a5944ad788028f0615e24e537350afe62a06b3..c340ea8255d32062aa8ea32149a0afdb8b2ceedf 100644
--- a/R/variant_classifier.R
+++ b/R/variant_classifier.R
@@ -134,7 +134,8 @@ variant_classifier <- function(
     ungroup() %>%
     dplyr::filter(rel_abundance > 0)
 
-  aa_info <- find_longest_reading_frames(unlist(unname(clustered_sequences))) %>%
+  aa_info <- find_longest_reading_frames(unlist(unname(
+                Biostrings::DNAStringSetList(clustered_sequences)))) %>%
     mutate(longest_aa_seq = max_width/3) %>%
     select(seqnames, longest_aa_seq)