diff --git a/iOS_SDK/OneSignalSDK/OneSignalCoreMocks/MockOneSignalClient.swift b/iOS_SDK/OneSignalSDK/OneSignalCoreMocks/MockOneSignalClient.swift
index b1b870f32..82f951094 100644
--- a/iOS_SDK/OneSignalSDK/OneSignalCoreMocks/MockOneSignalClient.swift
+++ b/iOS_SDK/OneSignalSDK/OneSignalCoreMocks/MockOneSignalClient.swift
@@ -32,7 +32,7 @@ public class MockOneSignalClient: NSObject, IOneSignalClient {
     let lock = NSLock()
 
     var mockResponses: [String: [String: Any]] = [:]
-    var mockFailureResponses: [String: NSError] = [:]
+    var mockFailureResponses: [String: OneSignalClientError] = [:]
     public var lastHTTPRequest: OneSignalRequest?
     public var networkRequestCount = 0
     public var executedRequests: [OneSignalRequest] = []
@@ -90,7 +90,7 @@ public class MockOneSignalClient: NSObject, IOneSignalClient {
         remoteParamsOutcomes = [:]
     }
 
-    public func execute(_ request: OneSignalRequest, onSuccess successBlock: @escaping OSResultSuccessBlock, onFailure failureBlock: @escaping OSFailureBlock) {
+    public func execute(_ request: OneSignalRequest, onSuccess successBlock: @escaping OSResultSuccessBlock, onFailure failureBlock: @escaping OSClientFailureBlock) {
         print("🧪 MockOneSignalClient execute called")
 
         if executeInstantaneously {
@@ -117,7 +117,7 @@ public class MockOneSignalClient: NSObject, IOneSignalClient {
         return stringified
     }
 
-    func finishExecutingRequest(_ request: OneSignalRequest, onSuccess successBlock: OSResultSuccessBlock, onFailure failureBlock: OSFailureBlock) {
+    func finishExecutingRequest(_ request: OneSignalRequest, onSuccess successBlock: OSResultSuccessBlock, onFailure failureBlock: OSClientFailureBlock) {
 
         // TODO: This entire method needs to contained within the equivalent of @synchronized ❗️
         print("🧪 completing HTTP request: \(request)")
@@ -137,8 +137,8 @@ public class MockOneSignalClient: NSObject, IOneSignalClient {
         }
         if (mockResponses[stringifiedRequest]) != nil {
             successBlock(mockResponses[stringifiedRequest])
-        } else if (mockFailureResponses[stringifiedRequest]) != nil {
-            failureBlock(mockFailureResponses[stringifiedRequest])
+        } else if let response = mockFailureResponses[stringifiedRequest] {
+            failureBlock(response)
         } else if fireSuccessForAllRequests {
             allRequestsHandled = false
             successBlock([:])
@@ -166,7 +166,7 @@ public class MockOneSignalClient: NSObject, IOneSignalClient {
         mockResponses[request] = response
     }
 
-    public func setMockFailureResponseForRequest(request: String, error: NSError) {
+    public func setMockFailureResponseForRequest(request: String, error: OneSignalClientError) {
         mockFailureResponses[request] = error
     }
 }
diff --git a/iOS_SDK/OneSignalSDK/OneSignalLiveActivitiesTests/OSLiveActivitiesExecutorTests.swift b/iOS_SDK/OneSignalSDK/OneSignalLiveActivitiesTests/OSLiveActivitiesExecutorTests.swift
index 9694d2667..b2af70b54 100644
--- a/iOS_SDK/OneSignalSDK/OneSignalLiveActivitiesTests/OSLiveActivitiesExecutorTests.swift
+++ b/iOS_SDK/OneSignalSDK/OneSignalLiveActivitiesTests/OSLiveActivitiesExecutorTests.swift
@@ -183,7 +183,7 @@ final class OSLiveActivitiesExecutorTests: XCTestCase {
         mockClient.reset()
 
         let request = OSRequestSetStartToken(key: "my-activity-type", token: "my-token")
-        mockClient.setMockFailureResponseForRequest(request: String(describing: request), error: NSError(domain: "not-important", code: 500))
+        mockClient.setMockFailureResponseForRequest(request: String(describing: request), error: OneSignalClientError(code: 500, message: "not-important", responseHeaders: nil, response: nil, underlyingError: nil))
 
         /* When */
         let executor = OSLiveActivitiesExecutor(requestDispatch: mockDispatchQueue)
@@ -210,7 +210,7 @@ final class OSLiveActivitiesExecutorTests: XCTestCase {
         mockClient.reset()
 
         let request = OSRequestSetStartToken(key: "my-activity-type", token: "my-token")
-        mockClient.setMockFailureResponseForRequest(request: String(describing: request), error: NSError(domain: "not-important", code: 401))
+        mockClient.setMockFailureResponseForRequest(request: String(describing: request), error: OneSignalClientError(code: 401, message: "not-important", responseHeaders: nil, response: nil, underlyingError: nil))
 
         /* When */
         let executor = OSLiveActivitiesExecutor(requestDispatch: mockDispatchQueue)
diff --git a/iOS_SDK/OneSignalSDK/OneSignalUserMocks/MockUserRequests.swift b/iOS_SDK/OneSignalSDK/OneSignalUserMocks/MockUserRequests.swift
index 77560bd28..7864d2905 100644
--- a/iOS_SDK/OneSignalSDK/OneSignalUserMocks/MockUserRequests.swift
+++ b/iOS_SDK/OneSignalSDK/OneSignalUserMocks/MockUserRequests.swift
@@ -108,7 +108,7 @@ extension MockUserRequests {
             fetchResponse = MockUserRequests.testIdentityPayload(onesignalId: osid, externalId: externalId)
             client.setMockFailureResponseForRequest(
                 request: "<OSRequestIdentifyUser with external_id: \(externalId)>",
-                error: NSError(domain: "not-important", code: 409)
+                error: OneSignalClientError(code: 409, message: "not-important", responseHeaders: nil, response: nil, underlyingError: nil)
             )
             // 2. Set the response for the subsequent Create User request
             let userResponse = MockUserRequests.testIdentityPayload(onesignalId: osid, externalId: externalId)