diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index b5eb886..af63c75 100644
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
@@ -236,6 +236,7 @@
 						        port start (wait until
 						        error-handling stage) */
 	AHCI_HFLAG_MULTI_MSI		= (1 << 16), /* multiple PCI MSIs */
+	AHCI_HFLAG_NO_DEVSLP		= (1 << 17), /* no device sleep */
 
 	/* ap->flags bits */