diff --git a/packages/shared/src/contracts/runtime.ts b/packages/shared/src/contracts/runtime.ts
index 3a39bd51f..49cc54e22 100644
--- a/packages/shared/src/contracts/runtime.ts
+++ b/packages/shared/src/contracts/runtime.ts
@@ -205,6 +205,7 @@ export type ProfileRechargeOrder = {
 
 export type ProfileRechargeCenterResponse = {
   walletBalance: number;
+  // TODO mirror backend: should not nullable
   mudPointBalance?: ProfileMudPointBalance;
   membership: ProfileMembership;
   pointProducts: ProfileRechargeProduct[];