diff --git a/ChangeLog b/ChangeLog
index ef7b7326e1..b8e438ecff 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6106,3 +6106,7 @@
 	  (2013-11-23)
 	* configs/sama5d3x-ek/src/sam_nand.c:  Add support for auto-mounting
 	  NAND MTD block or NXFFS devices (2013-11-25).
+	* include/mtd/mtd.h:  Packed the geometry structure so that it can
+	  support larger erase block sizes without increasing the size of
+	  the geometry structure (2013-11-27).
+
diff --git a/include/nuttx/mtd/mtd.h b/include/nuttx/mtd/mtd.h
index ab3f4608ba..dfd40edf7c 100644
--- a/include/nuttx/mtd/mtd.h
+++ b/include/nuttx/mtd/mtd.h
@@ -79,9 +79,9 @@
 
 struct mtd_geometry_s
 {
-  uint16_t blocksize;     /* Size of one read/write block */
-  uint16_t erasesize;     /* Size of one erase blocks -- must be a multiple
-                           * of blocksize. */
+  uint32_t blocksize :14; /* Size of one read/write block.  Largest: 16KB-1 */
+  uint32_t erasesize :18; /* Size of one erase blocks -- must be a multiple
+                           * of blocksize.  Largest: 512KB-1 */
   size_t neraseblocks;    /* Number of erase blocks */
 };