diff --git a/board/io4.c b/board/io4.c
index 79d7085..a549620 100644
--- a/board/io4.c
+++ b/board/io4.c
@@ -1,4 +1,6 @@
 #include <windows.h>
+
+#include <devioctl.h>
 #include <hidclass.h>
 
 #include <assert.h>