diff --git a/server/src/FileServerHandler.cpp b/server/src/FileServerHandler.cpp
index ad1d21b..4fb641d 100644
--- a/server/src/FileServerHandler.cpp
+++ b/server/src/FileServerHandler.cpp
@@ -46,21 +46,21 @@ void FileServerHandler::callback_transfer_registered(const std::shared_ptr<trans
 
     const auto bytes = transfer->expected_file_size - transfer->file_offset;
     if(transfer->direction == transfer::Transfer::DIRECTION_UPLOAD) {
-        server->properties()[property::VIRTUALSERVER_TOTAL_BYTES_UPLOADED] += bytes;
-        server->properties()[property::VIRTUALSERVER_MONTH_BYTES_UPLOADED] += bytes;
+        server->properties()[property::VIRTUALSERVER_TOTAL_BYTES_UPLOADED] += (int64_t) bytes;
+        server->properties()[property::VIRTUALSERVER_MONTH_BYTES_UPLOADED] += (int64_t) bytes;
     } else {
-        server->properties()[property::VIRTUALSERVER_TOTAL_BYTES_DOWNLOADED] += bytes;
-        server->properties()[property::VIRTUALSERVER_MONTH_BYTES_DOWNLOADED] += bytes;
+        server->properties()[property::VIRTUALSERVER_TOTAL_BYTES_DOWNLOADED] += (int64_t) bytes;
+        server->properties()[property::VIRTUALSERVER_MONTH_BYTES_DOWNLOADED] += (int64_t) bytes;
     }
 
     auto client = server->find_client_by_id(transfer->client_id);
     if(client && client->getUid() == transfer->client_unique_id) {
         if(transfer->direction == transfer::Transfer::DIRECTION_UPLOAD) {
-            client->properties()[property::CLIENT_TOTAL_BYTES_UPLOADED] += bytes;
-            client->properties()[property::CLIENT_MONTH_BYTES_UPLOADED] += bytes;
+            client->properties()[property::CLIENT_TOTAL_BYTES_UPLOADED] += (int64_t) bytes;
+            client->properties()[property::CLIENT_MONTH_BYTES_UPLOADED] += (int64_t) bytes;
         } else {
-            client->properties()[property::CLIENT_MONTH_BYTES_DOWNLOADED] += bytes;
-            client->properties()[property::CLIENT_MONTH_BYTES_DOWNLOADED] += bytes;
+            client->properties()[property::CLIENT_MONTH_BYTES_DOWNLOADED] += (int64_t) bytes;
+            client->properties()[property::CLIENT_MONTH_BYTES_DOWNLOADED] += (int64_t) bytes;
         }
     }
 }