diff --git a/include/linux/libata.h b/include/linux/libata.h
index ab5c726ad77baf6dbe7db8ea23203b9f219033a2..3f51f276915bc0e49a87b3de5c154168a908ebb5 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -503,6 +503,7 @@ 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 */