diff --git a/include/ntfs/layout.h b/include/ntfs/layout.h
index 9782f426..85cf8461 100644
--- a/include/ntfs/layout.h
+++ b/include/ntfs/layout.h
@@ -2111,14 +2111,10 @@ typedef struct {
 					   this must be COLLATION_FILE_NAME. */
 	u32 index_block_size;		/* Size of each index block in bytes (in
 					   the index allocation attribute). */
-	s8 clusters_per_index_block;	/* Cluster size of each index block (in
+	u8 clusters_per_index_block;	/* Cluster size of each index block (in
 					   the index allocation attribute), when
 					   an index block is >= than a cluster,
-					   otherwise this will be the -log of
-					   the size (like how the encoding of
-					   the mft record size and the index
-					   record size found in the boot sector
-					   work). Has to be a power of 2. */
+					   otherwise sectors per index block. */
 	u8 reserved[3];			/* Reserved/align to 8-byte boundary. */
 	INDEX_HEADER index;		/* Index header describing the
 					   following index entries. */
diff --git a/libntfs/dir.c b/libntfs/dir.c
index 3b157011..0d29bf30 100644
--- a/libntfs/dir.c
+++ b/libntfs/dir.c
@@ -1244,8 +1244,9 @@ static ntfs_inode *__ntfs_create(ntfs_inode *dir_ni,
 					ni->vol->indx_record_size >>
 					ni->vol->cluster_size_bits;
 		else
-			ir->clusters_per_index_block =
-					-ni->vol->indx_record_size_bits;
+			ir->clusters_per_index_block = 
+					ni->vol->indx_record_size >>
+					ni->vol->sector_size_bits;
 		ir->index.entries_offset = cpu_to_le32(sizeof(INDEX_HEADER));
 		ir->index.index_length = cpu_to_le32(index_len);
 		ir->index.allocated_size = cpu_to_le32(index_len);