1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index dc362fa01ca4..f6408ca82062 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3455,7 +3455,8 @@ static void ata_dev_xfermask(struct ata_device *dev)
                                "device is on DMA blacklist, disabling DMA\n");
         }
 
-        if ((host->flags & ATA_HOST_SIMPLEX) && host->simplex_claimed != ap) {
+        if ((host->flags & ATA_HOST_SIMPLEX) &&
+            host->simplex_claimed && host->simplex_claimed != ap) {
                 xfer_mask &= ~(ATA_MASK_MWDMA | ATA_MASK_UDMA);
                 ata_dev_printk(dev, KERN_WARNING, "simplex DMA is claimed by "
                                "other device, disabling DMA\n");