diff --git a/src/fileformat.proto b/src/fileformat.proto
index 7c1076d..54be8fe 100644
--- a/src/fileformat.proto
+++ b/src/fileformat.proto
@@ -11,16 +11,20 @@ package OSMPBF;
 message Blob {
   optional bytes raw = 1; // No compression
   optional int32 raw_size = 2; // When compressed, the uncompressed size
+
   // Possible compressed versions of the data.
   optional bytes zlib_data = 3;
-  optional bytes lzma_data = 4;
-  optional bytes bzip2_data = 5;
+
+  // PROPOSED feature for LZMA compressed data.
+  // optional bytes lzma_data = 4; // Do not change this tag number.
+
+  // Formerly used for bzip2 compressed data. Depreciated in 2010.
+  optional bytes OBSOLETE_bzip2_data = 5 [deprecated=true]; // Don't reuse this tag number.
 }
 
 /* A file contains an sequence of fileblock headers, each prefixed by
-their length, followed by a data block containing the actual data. 
-types staring with a "_" are reserved.
-
+their length in network byte order, followed by a data block
+containing the actual data. types staring with a "_" are reserved.
 */
 
 message BlockHeader {