diff --git a/src/Core/Abstractions/IApiService.cs b/src/Core/Abstractions/IApiService.cs
index 1d4ee9037..75cc565d6 100644
--- a/src/Core/Abstractions/IApiService.cs
+++ b/src/Core/Abstractions/IApiService.cs
@@ -47,7 +47,7 @@ namespace Bit.Core.Abstractions
         Task RefreshIdentityTokenAsync();
         Task<SsoPrevalidateResponse> PreValidateSso(string identifier);
         Task<TResponse> SendAsync<TRequest, TResponse>(HttpMethod method, string path,
-            TRequest body, bool authed, bool hasResponse, bool logoutOnUnauthorized = true);
+            TRequest body, bool authed, bool hasResponse, Action<HttpRequestMessage> alterRequest, bool logoutOnUnauthorized = true);
         void SetUrls(EnvironmentUrls urls);
         [Obsolete("Mar 25 2021: This method has been deprecated in favor of direct uploads. This method still exists for backward compatibility with old server versions.")]
         Task<CipherResponse> PostCipherAttachmentLegacyAsync(string id, MultipartFormDataContent data);
diff --git a/src/Core/Services/ApiService.cs b/src/Core/Services/ApiService.cs
index 7849951a2..66587b4a0 100644
--- a/src/Core/Services/ApiService.cs
+++ b/src/Core/Services/ApiService.cs
@@ -10,6 +10,7 @@ using Bit.Core.Exceptions;
 using Bit.Core.Models.Domain;
 using Bit.Core.Models.Request;
 using Bit.Core.Models.Response;
+using Bit.Core.Utilities;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
 using Newtonsoft.Json.Serialization;
@@ -183,13 +184,13 @@ namespace Bit.Core.Services
 
         public Task PostAccountRequestOTP()
         {
-            return SendAsync<object, object>(HttpMethod.Post, "/accounts/request-otp", null, true, false, false);
+            return SendAsync<object, object>(HttpMethod.Post, "/accounts/request-otp", null, true, false, null, false);
         }
 
         public Task PostAccountVerifyOTPAsync(VerifyOTPRequest request)
         {
             return SendAsync<VerifyOTPRequest, object>(HttpMethod.Post, "/accounts/verify-otp", request,
-                true, false, false);
+                true, false, null, false);
         }
 
         public Task PutUpdateTempPasswordAsync(UpdateTempPasswordRequest request)
@@ -570,7 +571,11 @@ namespace Bit.Core.Services
 
         public Task<bool> GetKnownDeviceAsync(string email, string deviceIdentifier)
         {
-            return SendAsync<object, bool>(HttpMethod.Get, $"/devices/knowndevice/{email}/{deviceIdentifier}", null, false, true);
+            return SendAsync<object, bool>(HttpMethod.Get, "/devices/knowndevice", null, false, true, (message) =>
+            {
+                message.Headers.Add("X-Device-Identifier", deviceIdentifier);
+                message.Headers.Add("X-Request-Email", CoreHelpers.Base64UrlEncode(Encoding.UTF8.GetBytes(email)));
+            });
         }
 
         #endregion
@@ -624,7 +629,7 @@ namespace Bit.Core.Services
         public Task<TResponse> SendAsync<TResponse>(HttpMethod method, string path, bool authed) =>
             SendAsync<object, TResponse>(method, path, null, authed, true);
         public async Task<TResponse> SendAsync<TRequest, TResponse>(HttpMethod method, string path, TRequest body,
-            bool authed, bool hasResponse, bool logoutOnUnauthorized = true)
+            bool authed, bool hasResponse, Action<HttpRequestMessage> alterRequest = null, bool logoutOnUnauthorized = true)
         {
             using (var requestMessage = new HttpRequestMessage())
             {
@@ -671,6 +676,7 @@ namespace Bit.Core.Services
                 {
                     requestMessage.Headers.Add("Accept", "application/json");
                 }
+                alterRequest?.Invoke(requestMessage);
 
                 HttpResponseMessage response;
                 try