diff --git a/drivers/ide/pci/ns87415.c b/drivers/ide/pci/ns87415.c
index 99e98e5..61a1436 100644
--- a/drivers/ide/pci/ns87415.c
+++ b/drivers/ide/pci/ns87415.c
@@ -160,8 +160,8 @@
 		new |= bit;
 
 	/* Select PIO or DMA, DMA may only be selected for one drive/channel. */
-	bit   = 1 << (20 + drive->select.b.unit       + (hwif->channel << 1));
-	other = 1 << (20 + (1 - drive->select.b.unit) + (hwif->channel << 1));
+	bit   = 1 << (20 + (drive->dn & 1) + (hwif->channel << 1));
+	other = 1 << (20 + (1 - (drive->dn & 1)) + (hwif->channel << 1));
 	new = use_dma ? ((new & ~other) | bit) : (new & ~bit);
 
 	if (new != *old) {