diff --git a/coding/blob_indexer.cpp b/coding/blob_indexer.cpp
index 05912e6ab4..ad7d35f584 100644
--- a/coding/blob_indexer.cpp
+++ b/coding/blob_indexer.cpp
@@ -13,7 +13,7 @@
 
 BlobIndexer::BlobIndexer(Writer & writer,
                          size_t maxUncompressedChunkSize,
-                         function<void (char const *, size_t, string &)> const & compressor) :
+                         CompressorType const & compressor) :
   m_writer(writer),
   m_maxUncompressedChunkSize(min(int(maxUncompressedChunkSize), (1 << BITS_IN_CHUNK_SIZE) - 1)),
   m_compressor(compressor),
diff --git a/coding/blob_indexer.hpp b/coding/blob_indexer.hpp
index 4aaa247028..3f23c1e3cc 100644
--- a/coding/blob_indexer.hpp
+++ b/coding/blob_indexer.hpp
@@ -9,9 +9,11 @@ class Writer;
 class BlobIndexer
 {
 public:
+  typedef function<void (char const *, size_t, string &)> CompressorType;
+
   BlobIndexer(Writer & writer,
               size_t maxUncompressedChunkSize,
-              function<void (char const *, size_t, string &)> const & compressor);
+              CompressorType const & compressor);
   ~BlobIndexer();
 
   // Add blob and return its id.
@@ -24,7 +26,7 @@ private:
 
   Writer & m_writer;
   size_t const m_maxUncompressedChunkSize;
-  function<void (char const *, size_t, string &)> const m_compressor;
+  CompressorType m_compressor;
 
   static uint32_t const BITS_IN_CHUNK_SIZE = 20;
 
diff --git a/coding/blob_storage.cpp b/coding/blob_storage.cpp
index 0838838e98..d35f7e13ba 100644
--- a/coding/blob_storage.cpp
+++ b/coding/blob_storage.cpp
@@ -6,7 +6,8 @@
 // nb - number of blobs
 // nc - number of chunks
 //
-// [4| Header = "Blb1"]
+// [3| Header = "Blb"]
+// [1| logMaxChunkSize]
 // [*| Chunk 0    ] [*| Chunk 1    ] ... [*| Chunk nc-1]
 // [4| Chunk 1 pos] [4| Chunk 2 pos] ... [4| Pos after the last chunk]
 // [4| Blob info 0] [4| Blob info 1] ... [4| Blob info nb-1]
@@ -23,7 +24,7 @@
 
 
 BlobStorage::BlobStorage(Reader const * pReader,
-                         function<void (char const *, size_t, char *, size_t)> decompressor) :
+                         DecompressorType const & decompressor) :
   m_pReader(pReader), m_decompressor(decompressor)
 {
   Init();
diff --git a/coding/blob_storage.hpp b/coding/blob_storage.hpp
index e1aa0ba194..e909f74e34 100644
--- a/coding/blob_storage.hpp
+++ b/coding/blob_storage.hpp
@@ -14,9 +14,11 @@ class BlobStorage
 public:
   DECLARE_EXCEPTION(OpenException, RootException);
 
+  typedef function<void (char const *, size_t, char *, size_t)> DecompressorType;
+
   // Takes ownership of pReader and deletes it, even if exception is thrown.
   BlobStorage(Reader const * pReader,
-              function<void (char const *, size_t, char *, size_t)> decompressor);
+              DecompressorType const & decompressor);
   ~BlobStorage();
 
   // Get blob by its number, starting from 0.
@@ -35,7 +37,7 @@ private:
   static uint32_t const START_OFFSET = 4;
 
   scoped_ptr<Reader const> m_pReader;
-  function<void (char const *, size_t, char *, size_t)> m_decompressor;
+  DecompressorType m_decompressor;
 
   DDVector<uint32_t, PolymorphReader> m_blobInfo;
   DDVector<uint32_t, PolymorphReader> m_chunkOffset;