diff --git a/Notesnook.API/Services/S3Service.cs b/Notesnook.API/Services/S3Service.cs
index a4619b1..d940d1b 100644
--- a/Notesnook.API/Services/S3Service.cs
+++ b/Notesnook.API/Services/S3Service.cs
@@ -230,7 +230,7 @@ namespace Notesnook.API.Services
             if (userId == null || objectName == null) throw new Exception("Could not abort multipart upload.");
 
             var subscriptionService = await WampServers.SubscriptionServer.GetServiceAsync<IUserSubscriptionService>(SubscriptionServerTopics.UserSubscriptionServiceTopic);
-            var subscription = await subscriptionService.GetUserSubscriptionAsync(Clients.Notesnook.Id, userId);
+            var subscription = await subscriptionService.GetUserSubscriptionAsync(Clients.Notesnook.Id, userId) ?? throw new Exception("User subscription not found.");
 
             long fileSize = await GetMultipartUploadSizeAsync(userId, uploadRequest.Key, uploadRequest.UploadId);
             if (StorageHelper.IsFileSizeExceeded(subscription, fileSize))
diff --git a/Notesnook.API/Services/UserService.cs b/Notesnook.API/Services/UserService.cs
index cc853b8..54f311b 100644
--- a/Notesnook.API/Services/UserService.cs
+++ b/Notesnook.API/Services/UserService.cs
@@ -118,7 +118,7 @@ namespace Notesnook.API.Services
             else
             {
                 var subscriptionService = await WampServers.SubscriptionServer.GetServiceAsync<IUserSubscriptionService>(SubscriptionServerTopics.UserSubscriptionServiceTopic);
-                subscription = await subscriptionService.GetUserSubscriptionAsync(Clients.Notesnook.Id, userId);
+                subscription = await subscriptionService.GetUserSubscriptionAsync(Clients.Notesnook.Id, userId) ?? throw new Exception("User subscription not found.");
             }
 
             var userSettings = await Repositories.UsersSettings.FindOneAsync((u) => u.UserId == user.UserId) ?? throw new Exception("User settings not found.");