diff --git a/lib/buyer.ts b/lib/buyer.ts
index 4a279ff..cc23cc4 100644
--- a/lib/buyer.ts
+++ b/lib/buyer.ts
@@ -57,7 +57,7 @@ export interface Buyer extends Resource {
 
 export class BuyerEndpoint extends Endpoint<Buyer> {
     constructor(marketplace: MarketplaceEndpoint, id: string) {
-        super(marketplace.base + `/buyers/${id}`, marketplace.apiKey);
+        super(marketplace.base + `/buyers/${id}`, marketplace.apiKey, marketplace.apiSecret);
     }
 
     async get() {
diff --git a/lib/endpoint.ts b/lib/endpoint.ts
index 58ca593..4b3c568 100644
--- a/lib/endpoint.ts
+++ b/lib/endpoint.ts
@@ -15,7 +15,7 @@ enum StatusClass {
 }
 
 export abstract class Endpoint<T extends Resource = AnyResource> {
-    constructor(readonly base: string, readonly apiKey: string) { }
+    constructor(readonly base: string, readonly apiKey: string, readonly apiSecret: string) { }
 
     private static statusClass(statusCode: number): StatusClass {
         return Math.floor(statusCode / 100);
@@ -31,7 +31,7 @@ export abstract class Endpoint<T extends Resource = AnyResource> {
 
     public async request<U extends Resource = T>(method: string, route: string = '', payload?: object): Promise<U | undefined> {
         const headers = new Headers({
-            Authorization: `Basic ${btoa(`${this.apiKey}:${this.apiKey}`)}`,
+            Authorization: `Basic ${btoa(`${this.apiKey}:${this.apiSecret}`)}`,
         });
 
         let uri;
diff --git a/lib/marketplace.ts b/lib/marketplace.ts
index afc40e8..4431f12 100644
--- a/lib/marketplace.ts
+++ b/lib/marketplace.ts
@@ -36,7 +36,7 @@ export interface Marketplace extends Resource {
 
 export class MarketplaceEndpoint extends Endpoint<Marketplace> {
     constructor(zoop: Zoop, id: string) {
-        super(zoop.base + `/marketplaces/${id}`, zoop.apiKey);
+        super(zoop.base + `/marketplaces/${id}`, zoop.apiKey, zoop.apiSecret);
     }
 
     buyer(id: string): BuyerEndpoint {
diff --git a/lib/seller.ts b/lib/seller.ts
index 51633d6..a24c67b 100644
--- a/lib/seller.ts
+++ b/lib/seller.ts
@@ -12,7 +12,7 @@ export interface Seller extends Resource {
 
 export class SellerEndpoint extends Endpoint<Seller> {
     constructor(marketplace: MarketplaceEndpoint, id: string) {
-        super(marketplace.base + `/sellers/${id}`, marketplace.apiKey);
+        super(marketplace.base + `/sellers/${id}`, marketplace.apiKey, marketplace.apiSecret);
     }
 
     async get() {
diff --git a/lib/token.ts b/lib/token.ts
index 1d930a8..87c8a14 100644
--- a/lib/token.ts
+++ b/lib/token.ts
@@ -44,7 +44,7 @@ export type Token = BankAccountToken | CardToken;
 
 export class TokenEndpoint extends Endpoint<Token> {
     constructor(marketplace: MarketplaceEndpoint, id: string) {
-        super(marketplace.base + `/tokens/${id}`, marketplace.apiKey);
+        super(marketplace.base + `/tokens/${id}`, marketplace.apiKey, marketplace.apiSecret);
     }
 
     async get() {
diff --git a/lib/transaction.ts b/lib/transaction.ts
index 01f65a8..3191cff 100644
--- a/lib/transaction.ts
+++ b/lib/transaction.ts
@@ -56,7 +56,7 @@ export interface Transaction extends Resource {
 
 export class TransactionEndpoint extends Endpoint<Transaction> {
     constructor(marketplace: MarketplaceEndpoint, id: string) {
-        super(marketplace.base + `/transactions/${id}`, marketplace.apiKey);
+        super(marketplace.base + `/transactions/${id}`, marketplace.apiKey, marketplace.apiSecret);
     }
 
     async get() {
diff --git a/lib/zoop.ts b/lib/zoop.ts
index 05dd2f5..bac9416 100644
--- a/lib/zoop.ts
+++ b/lib/zoop.ts
@@ -5,8 +5,8 @@ import { AnyResource, Resource } from './resource';
 const API_BASE = 'https://api.zoop.ws/v1';
 
 export class Zoop extends Endpoint {
-    constructor(readonly apiKey: string) {
-        super(API_BASE, apiKey);
+    constructor(readonly apiKey: string, readonly apiSecret: string = apiKey) {
+        super(API_BASE, apiKey, apiSecret);
     }
 
     marketplace(id: string) {