diff --git a/Sources/SwiftyStoreKit/ProductsInfoController.swift b/Sources/SwiftyStoreKit/ProductsInfoController.swift
index e54d065f..32371a03 100644
--- a/Sources/SwiftyStoreKit/ProductsInfoController.swift
+++ b/Sources/SwiftyStoreKit/ProductsInfoController.swift
@@ -49,7 +49,20 @@ class ProductsInfoController: NSObject {
     }
     
     // As we can have multiple inflight requests, we store them in a dictionary by product ids
-    private var inflightRequests: [Set<String>: InAppProductQuery] = [:]
+    private var inflightRequestsStorage: [Set<String>: InAppProductQuery] = [:]
+    private let requestsQueue = DispatchQueue(label: "inflightRequestsQueue", attributes: .concurrent)
+    private var inflightRequests: [Set<String>: InAppProductQuery] {
+        get {
+            requestsQueue.sync {
+                inflightRequestsStorage
+            }
+        }
+        set {
+            requestsQueue.sync(flags: .barrier) {
+                inflightRequestsStorage = newValue
+            }
+        }
+    }
 
     @discardableResult
     func retrieveProductsInfo(_ productIds: Set<String>, completion: @escaping (RetrieveResults) -> Void) -> InAppProductRequest {
diff --git a/SwiftyStoreKit-iOS-Demo/ViewController.swift b/SwiftyStoreKit-iOS-Demo/ViewController.swift
index fa640325..a690403a 100644
--- a/SwiftyStoreKit-iOS-Demo/ViewController.swift
+++ b/SwiftyStoreKit-iOS-Demo/ViewController.swift
@@ -279,6 +279,8 @@ extension ViewController {
         case .success(let purchase):
             print("Purchase Success: \(purchase.productId)")
             return nil
+        case .deferred(purchase: _):
+            return alertWithTitle("Purchase deferred", message: "The purchase deferred")
         case .error(let error):
             print("Purchase Failed: \(error)")
             switch error.code {
diff --git a/SwiftyStoreKit-macOS-Demo/ViewController.swift b/SwiftyStoreKit-macOS-Demo/ViewController.swift
index 071c6d9f..d0eaf729 100644
--- a/SwiftyStoreKit-macOS-Demo/ViewController.swift
+++ b/SwiftyStoreKit-macOS-Demo/ViewController.swift
@@ -193,6 +193,8 @@ extension ViewController {
         case .success(let purchase):
             print("Purchase Success: \(purchase.productId)")
             return alertWithTitle("Thank You", message: "Purchase completed")
+        case .deferred(purchase: _):
+            return alertWithTitle("Purchase deferred", message: "The purchase deferred")
         case .error(let error):
             print("Purchase Failed: \(error)")
             switch error.code {
diff --git a/Tests/SwiftyStoreKitTests/ProductsInfoControllerTests.swift b/Tests/SwiftyStoreKitTests/ProductsInfoControllerTests.swift
index 3343be52..99ccc26f 100644
--- a/Tests/SwiftyStoreKitTests/ProductsInfoControllerTests.swift
+++ b/Tests/SwiftyStoreKitTests/ProductsInfoControllerTests.swift
@@ -54,11 +54,21 @@ class TestInAppProductRequest: InAppProductRequest {
 
 class TestInAppProductRequestBuilder: InAppProductRequestBuilder {
     
-    var requests: [ TestInAppProductRequest ] = []
+    private var _requests: [TestInAppProductRequest] = []
+    private let requestsQueue = DispatchQueue(label: "builderRequestsQueue", attributes: .concurrent)
+    var requests: [ TestInAppProductRequest ] {
+        get {
+            requestsQueue.sync {
+                _requests
+            }
+        }
+    }
     
     func request(productIds: Set<String>, callback: @escaping InAppProductRequestCallback) -> InAppProductRequest {
         let request = TestInAppProductRequest(productIds: productIds, callback: callback)
-        requests.append(request)
+        requestsQueue.sync(flags: .barrier) {
+          _requests.append(request)
+        }
         return request
     }
     
@@ -66,7 +76,7 @@ class TestInAppProductRequestBuilder: InAppProductRequestBuilder {
         requests.forEach {
             $0.fireCallback()
         }
-        requests = []
+        _requests = []
     }
 }
 
@@ -143,25 +153,28 @@ class ProductsInfoControllerTests: XCTestCase {
     // Create the expectation not to let the test finishes before the other threads complete
     let expectation = XCTestExpectation(description: "Expect downloads of product informations")
     
-    // Create the dispatch group to let the test verifies the assert only when
+    // Create the dispatch groups to let the test verifies the assert only when
     // everything else finishes.
-    let group = DispatchGroup()
+    let groupCompletion = DispatchGroup()
+    let groupFire = DispatchGroup()
     
     // Dispatch a request for every product in a different thread
     for product in testProducts {
+      groupCompletion.enter()
+      groupFire.enter()
       DispatchQueue.global().async {
-        group.enter()
         productInfoController.retrieveProductsInfo([product]) { _ in
           completionCallbackCount += 1
-          group.leave()
+          groupCompletion.leave()
         }
+        groupFire.leave()
       }
     }
-    DispatchQueue.global().asyncAfter(deadline: .now()+0.1) {
+    groupFire.notify(queue: DispatchQueue.global()) {
       requestBuilder.fireCallbacks()
     }
     // Fullfil the expectation when every thread finishes
-    group.notify(queue: DispatchQueue.global()) {
+    groupCompletion.notify(queue: DispatchQueue.global()) {
       
       XCTAssertEqual(completionCallbackCount, self.testProducts.count)
       expectation.fulfill()