diff --git a/tz.cpp b/tz.cpp
index c6f7e6b..d8ebed4 100644
--- a/tz.cpp
+++ b/tz.cpp
@@ -182,7 +182,7 @@ get_known_folder(const GUID& folderid)
 {
     std::string folder;
     PWSTR pfolder = nullptr;
-    HRESULT hr = SHGetKnownFolderPath(folderid, KF_FLAG_DEFAULT, NULL, &pfolder);
+    HRESULT hr = SHGetKnownFolderPath(folderid, KF_FLAG_DEFAULT, nullptr, &pfolder);
     if (SUCCEEDED(hr))
     {
         co_task_mem_ptr folder_ptr(pfolder);