diff --git a/include/ata.h b/include/ata.h
index b51475d..3b2d737 100644
--- a/include/ata.h
+++ b/include/ata.h
@@ -82,7 +82,9 @@
 /*
  * Device / Head Register Bits
  */
+#ifndef ATA_DEVICE
 #define ATA_DEVICE(x)	((x & 1)<<4)
+#endif /* ATA_DEVICE */
 #define ATA_LBA		0xE0
 
 /*