diff --git a/src/app/api/sites/[id]/route.ts b/src/app/api/sites/[id]/route.ts
index d1d94d0..e312c75 100644
--- a/src/app/api/sites/[id]/route.ts
+++ b/src/app/api/sites/[id]/route.ts
@@ -37,6 +37,7 @@ export async function PATCH(
     "work_hours",
     "hours_per_week",
     "wages_hours_per_day",
+    "work_month_start_day",
   ] as const) {
     const v = body[k];
     if (v === null || v === "") continue;
diff --git a/src/app/api/sites/route.ts b/src/app/api/sites/route.ts
index f0471c1..2a8004f 100644
--- a/src/app/api/sites/route.ts
+++ b/src/app/api/sites/route.ts
@@ -39,6 +39,7 @@ export async function POST(request: Request) {
     "hours_per_week",
     "wages_hours_per_day",
     "job_start_date",
+    "work_month_start_day",
   ]) {
     if (body[key] !== undefined && body[key] !== null && body[key] !== "") {
       payload[key] = body[key];
@@ -50,6 +51,7 @@ export async function POST(request: Request) {
     "work_hours",
     "hours_per_week",
     "wages_hours_per_day",
+    "work_month_start_day",
   ]) {
     if (typeof payload[key] === "string" && payload[key] === "") {
       delete payload[key];