diff --git a/src/qt/win_cdrom_ioctl.c b/src/qt/win_cdrom_ioctl.c
index 271f7226f..38c553852 100644
--- a/src/qt/win_cdrom_ioctl.c
+++ b/src/qt/win_cdrom_ioctl.c
@@ -30,6 +30,7 @@
 #include <stdint.h>
 #include <string.h>
 #include <stdlib.h>
+#include <stddef.h>
 #include <wchar.h>
 #include <86box/cdrom.h>
 #include <86box/log.h>