diff --git a/atst/forms/ko_review.py b/atst/forms/ko_review.py
index c92561ab..c50deed7 100644
--- a/atst/forms/ko_review.py
+++ b/atst/forms/ko_review.py
@@ -31,7 +31,8 @@ class KOReviewForm(CacheableForm):
     )
     loas = FieldList(
         StringField(
-            translate("forms.ko_review.loa"), validators=[Length(min=10), IsNumber()]
+            translate("forms.ko_review.loa"),
+            validators=[Length(min=10), IsNumber(), Optional()],
         )
     )
     custom_clauses = TextAreaField(