diff --git a/libc/kernel/uapi/linux/can.h b/libc/kernel/uapi/linux/can.h
index 0fc98ae..a913d73 100644
--- a/libc/kernel/uapi/linux/can.h
+++ b/libc/kernel/uapi/linux/can.h
@@ -55,6 +55,9 @@
 };
 #define CANXL_XLF 0x80
 #define CANXL_SEC 0x01
+#define CANXL_VCID_OFFSET 16
+#define CANXL_VCID_VAL_MASK 0xFFUL
+#define CANXL_VCID_MASK (CANXL_VCID_VAL_MASK << CANXL_VCID_OFFSET)
 struct canxl_frame {
   canid_t prio;
   __u8 flags;