diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index cef85e515c4c..9ddb568267e1 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -1142,8 +1142,11 @@ static int ata_bus_probe(struct ata_port *ap)
 
 		rc = ap->ops->probe_reset(ap, classes);
 		if (rc == 0) {
-			for (i = 0; i < ATA_MAX_DEVICES; i++)
+			for (i = 0; i < ATA_MAX_DEVICES; i++) {
+				if (classes[i] == ATA_DEV_UNKNOWN)
+					classes[i] = ATA_DEV_NONE;
 				ap->device[i].class = classes[i];
+			}
 		} else {
 			printk(KERN_ERR "ata%u: probe reset failed, "
 			       "disabling port\n", ap->id);