diff --git a/packages/client/src/forms/register/mappings/event-specific-fields/death/mutation/deceased-mappings.ts b/packages/client/src/forms/register/mappings/event-specific-fields/death/mutation/deceased-mappings.ts
index 2c5ca03f35..da596bbd8c 100644
--- a/packages/client/src/forms/register/mappings/event-specific-fields/death/mutation/deceased-mappings.ts
+++ b/packages/client/src/forms/register/mappings/event-specific-fields/death/mutation/deceased-mappings.ts
@@ -39,9 +39,9 @@ export const fieldToDeceasedDateTransformation =
       fieldValue = clonedTransformedData[sectionId][field.name]
     }
 
-    transformedData[
-      alternativeSectionId ? alternativeSectionId : sectionId
-    ].deceased = {
+    transformedData[alternativeSectionId ?? sectionId] ??= {}
+
+    transformedData[alternativeSectionId ?? sectionId].deceased = {
       deceased: true,
       deathDate: fieldValue
     }