diff --git a/drivers/ata/pata_ali.c b/drivers/ata/pata_ali.c
index 76e3860..fde5ce9 100644
--- a/drivers/ata/pata_ali.c
+++ b/drivers/ata/pata_ali.c
@@ -153,11 +153,11 @@
 
 static unsigned long ali_20_filter(const struct ata_port *ap, struct ata_device *adev, unsigned long mask)
 {
-	char model_num[ATA_ID_PROD_LEN];
+	char model_num[ATA_ID_PROD_LEN + 1];
 	/* No DMA on anything but a disk for now */
 	if (adev->class != ATA_DEV_ATA)
 		mask &= ~(ATA_MASK_MWDMA | ATA_MASK_UDMA);
-	ata_id_string(adev->id, model_num, ATA_ID_PROD, sizeof(model_num));
+	ata_id_c_string(adev->id, model_num, ATA_ID_PROD, sizeof(model_num));
 	if (strstr(model_num, "WDC"))
 		return mask &= ~ATA_MASK_UDMA;
 	return ata_pci_default_filter(ap, adev, mask);