diff --git a/gptpart.h b/gptpart.h
index f62d5b5..657b3f9 100644
--- a/gptpart.h
+++ b/gptpart.h
@@ -25,6 +25,11 @@
 
 using namespace std;
 
+// Values returned by GPTPart::IsSizedForMBR()
+#define MBR_SIZED_GOOD 0 /* Whole partition under 2^32 sectors */
+#define MBR_SIZED_IFFY 1 /* Partition starts under 2^32 & is less than 2^32, but ends over 2^32 */
+#define MBR_SIZED_BAD  2 /* Partition starts over 2^32, is bigger than 2^32, or otherwise bad */
+
 /****************************************
  *                                      *
  * GPTPart class and related structures *