diff --git a/libs/pbd/pbd/crossthread.h b/libs/pbd/pbd/crossthread.h
index fd9c9f8eeb..6167c664db 100644
--- a/libs/pbd/pbd/crossthread.h
+++ b/libs/pbd/pbd/crossthread.h
@@ -29,7 +29,7 @@
 #include "pbd/libpbd_visibility.h"
 
 #ifdef PLATFORM_WINDOWS
-#include <Windows.h>
+#include <windows.h>
 #endif // PLATFORM_WINDOWS