diff --git a/backend/src/graphql/arg/CreateUserArgs.ts b/backend/src/graphql/arg/CreateUserArgs.ts
index 710c52f6d..af915b91a 100644
--- a/backend/src/graphql/arg/CreateUserArgs.ts
+++ b/backend/src/graphql/arg/CreateUserArgs.ts
@@ -18,5 +18,5 @@ export default class CreateUserArgs {
   publisherId: number
 
   @Field(() => String, { nullable: true })
-  redeemCode: string | null
+  redeemCode?: string | null
 }