diff --git a/src/pages/admin/signups/[id].tsx b/src/pages/admin/signups/[id].tsx
index 16cafb0..7135748 100644
--- a/src/pages/admin/signups/[id].tsx
+++ b/src/pages/admin/signups/[id].tsx
@@ -102,16 +102,15 @@ const SignupCreatePage: NextPage = () => {
 
   const router = useRouter();
 
-  let id: string;
+  let id: number;
 
   if (router.query?.id && router.query.id !== "create") {
-    id = router.query.id as string;
+    id = Number(router.query.id);
   }
 
   useEffect(() => {
-    const suId = id && Number(id);
-    if (suId !== undefined) {
-      SignupApi.getForm(suId, true)
+    if (!Number.isNaN(id)) {
+      SignupApi.getForm(id, true)
         .then((res) => {
           setFormData({
             ...res,