diff --git a/ConcurrentLinuxSr.md b/ConcurrentLinuxSr.md
index f6d111b..32f2193 100644
--- a/ConcurrentLinuxSr.md
+++ b/ConcurrentLinuxSr.md
@@ -94,6 +94,10 @@ function `sr_block_ioctl()` in case of SG_IO:
 static int sr_block_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
                           unsigned long arg)
 {
+...
+#include <scsi/sg.h>            /* For number value of ioctl cmd SG_IO */
+...
+
        ...
        if (cmd != SG_IO)
                mutex_lock(&sr_mutex);