diff --git a/include/linux/libata.h b/include/linux/libata.h
index e752368ea351..6346272432ff 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -486,6 +486,7 @@ enum hsm_task_states {
 };
 
 enum ata_completion_errors {
+	AC_ERR_OK		= 0,	    /* no error */
 	AC_ERR_DEV		= (1 << 0), /* device reported error */
 	AC_ERR_HSM		= (1 << 1), /* host state machine violation */
 	AC_ERR_TIMEOUT		= (1 << 2), /* timeout */