diff --git a/fs/befs/datastream.h b/fs/befs/datastream.h
index 45e8a3c..91ba820 100644
--- a/fs/befs/datastream.h
+++ b/fs/befs/datastream.h
@@ -4,16 +4,17 @@
  */
 
 struct buffer_head *befs_read_datastream(struct super_block *sb,
-					 befs_data_stream * ds, befs_off_t pos,
-					 uint * off);
+					 const befs_data_stream *ds,
+					 befs_off_t pos, uint * off);
 
-int befs_fblock2brun(struct super_block *sb, befs_data_stream * data,
+int befs_fblock2brun(struct super_block *sb, const befs_data_stream *data,
 		     befs_blocknr_t fblock, befs_block_run * run);
 
-size_t befs_read_lsymlink(struct super_block *sb, befs_data_stream * data,
+size_t befs_read_lsymlink(struct super_block *sb, const befs_data_stream *data,
 			  void *buff, befs_off_t len);
 
-befs_blocknr_t befs_count_blocks(struct super_block *sb, befs_data_stream * ds);
+befs_blocknr_t befs_count_blocks(struct super_block *sb,
+			  const befs_data_stream *ds);
 
 extern const befs_inode_addr BAD_IADDR;