diff --git a/src/modules/app.ts b/src/modules/app.ts
index 007b5df..50bb1f4 100644
--- a/src/modules/app.ts
+++ b/src/modules/app.ts
@@ -30,9 +30,9 @@ export default class App extends ModuleBase {
     const value = this.buildSetFunctionValue(depositParam);
     const funcOp = buildSetOperation("SET_FUNCTION", depositParam.ref, value);
     setFunctionOps.push(funcOp);
-  
+    const depositAddress = this.getDefaultAccount().address;
     const defaultConfig: appBillingConfig = {
-      depositAddress: this.ain.wallet.defaultAccount!.address,
+      depositAddress,
       service: {
         default: {
           costPerToken: 0,
@@ -149,11 +149,7 @@ export default class App extends ModuleBase {
 
   private buildCreateAppOp(appName: string): SetOperation {
     const path = `/manage_app/${appName}/create/${Date.now()}`;
-    const adminAccount = this.ain.wallet.defaultAccount!;
-    if (!adminAccount || !adminAccount.address) {
-      // FIXME(yoojin): change Error to Custom error when it added.
-      throw new Error("You need to enter your private key when initialize sdk.");
-    }
+    const adminAccount = this.getDefaultAccount();
     const value = {
       admin: {
         [adminAccount.address]: true,
diff --git a/src/modules/moduleBase.ts b/src/modules/moduleBase.ts
index 6fa0c23..163d948 100644
--- a/src/modules/moduleBase.ts
+++ b/src/modules/moduleBase.ts
@@ -21,6 +21,13 @@ export default class ModuleBase {
     }
   }
 
+  protected getDefaultAccount() {
+    const defaultAccount = this.ain.wallet.defaultAccount;
+    if (!defaultAccount) 
+      throw new Error("You need to set default account.");
+    return defaultAccount;
+  }
+
   private async _sendTransaction(txBody: TransactionBody) {
     return await this.ain.sendTransaction(txBody);
   }
diff --git a/src/modules/service/depositService.ts b/src/modules/service/depositService.ts
index 5e9b6ad..f2f3bca 100644
--- a/src/modules/service/depositService.ts
+++ b/src/modules/service/depositService.ts
@@ -7,7 +7,7 @@ import { HISTORY_TYPE } from "../../types/type";
 export default class DepositService extends ServiceBase {
   async requestDeposit(appName: string, amount: number, userAddress?: string) {
     const transferKey = Date.now();
-    userAddress = userAddress ? userAddress : this.wallet.getDefaultAccount();
+    userAddress = userAddress ? userAddress : this.wallet.getDefaultAddress();
     const depositAddress = await this.getDepositAddress(appName);
 
     const op_list: SetOperation[]  = [
diff --git a/src/modules/service/useService.ts b/src/modules/service/useService.ts
index 991231c..0fa93fe 100644
--- a/src/modules/service/useService.ts
+++ b/src/modules/service/useService.ts
@@ -7,7 +7,7 @@ import ServiceBase from "./serviceBase";
 export default class UseService extends ServiceBase{
   async writeRequest(appName: string, serviceName: string, value: string, requesterAddress?: string) {
     const requestKey = Date.now();
-    requesterAddress = requesterAddress ? requesterAddress : this.wallet.getDefaultAccount();
+    requesterAddress = requesterAddress ? requesterAddress : this.wallet.getDefaultAddress();
     const requestPath = Path.app(appName).request(serviceName, requesterAddress, requestKey);
     const requestData = {
       prompt: value,
@@ -19,7 +19,7 @@ export default class UseService extends ServiceBase{
   }
 
   async calculateCostAndCheckBalance(appName: string, serviceName: string, value: string, requesterAddress?: string) {
-    requesterAddress = requesterAddress ? requesterAddress : this.wallet.getDefaultAccount();
+    requesterAddress = requesterAddress ? requesterAddress : this.wallet.getDefaultAddress();
     const billingConfig = await this.app.getBillingConfig(appName);
     // TODO(woojae): calculate cost more accurately
     let serviceBillingConfig = billingConfig.service.default;
diff --git a/src/modules/wallet.ts b/src/modules/wallet.ts
index eb23349..e585072 100644
--- a/src/modules/wallet.ts
+++ b/src/modules/wallet.ts
@@ -13,11 +13,8 @@ export default class Wallet extends ModuleBase{
    * Get defult AI Network blockchain account information set in ainize.
    * @returns Default account's address.
    */
-  getDefaultAccount() {
-    if (!this.ain.wallet.defaultAccount) {
-      throw new Error("You need to set default account.");
-    }
-    return this.ain.wallet.defaultAccount.address;
+  getDefaultAddress() {
+    return this.getDefaultAccount().address;
   }
 
   /**
@@ -27,7 +24,7 @@ export default class Wallet extends ModuleBase{
    */
   setDefaultAccount(privateKey: string) {
     this.ain.wallet.addAndSetDefaultAccount(privateKey);
-    return this.getDefaultAccount();
+    return this.getDefaultAddress();
   }
 
   /**
@@ -46,7 +43,7 @@ export default class Wallet extends ModuleBase{
    */
   getAinBalance(address?: string) {
     if (!address) {
-      address = this.getDefaultAccount();
+      address = this.getDefaultAddress();
     }
     return this.ain.wallet.getBalance(address);
   }
@@ -59,7 +56,7 @@ export default class Wallet extends ModuleBase{
    */
   async sendTxWithAddress(txBody: TransactionInput, signerAddress?: string) {
     if (!signerAddress) {
-      signerAddress = this.getDefaultAccount();
+      signerAddress = this.getDefaultAddress();
     }
     if (!this.ain.wallet.isAdded(signerAddress)) {
       throw new Error ("You need to add account");