diff --git a/include/btreeheader.h b/include/btreeheader.h
index e5061ee..2aa7267 100644
--- a/include/btreeheader.h
+++ b/include/btreeheader.h
@@ -5,7 +5,8 @@
   uInt32 treeDepth;
   uInt32 treeWidth;
   uInt32 treeLeafCount;
-  uInt32 firstDeleted;
+  uInt32 firstNodeOffset; // used when tree is on disk
+  int32  firstDeleted;    // used to point to an empty node
 } bTreeHeader; // bTreeHeader
 
 #endif /* !BTREEHEADER_H */