diff --git a/gene_splicer/utils.py b/gene_splicer/utils.py
index 4985ba5..e7693ae 100644
--- a/gene_splicer/utils.py
+++ b/gene_splicer/utils.py
@@ -405,6 +405,7 @@ def align(target_seq,
         return alignment_path
 
 HIVINTACT_ERRORS_TABLE = [
+    'UnknownNucleotide',
     'NonHIV',
     'LongDeletion',
     'InternalInversion',