diff --git a/platform/chunks_download_strategy.cpp b/platform/chunks_download_strategy.cpp
index 06c0ac6a73..6e24acb73b 100644
--- a/platform/chunks_download_strategy.cpp
+++ b/platform/chunks_download_strategy.cpp
@@ -1,7 +1,5 @@
 #include "chunks_download_strategy.hpp"
 
-#include "../defines.hpp"
-
 #include "../coding/file_writer.hpp"
 #include "../coding/file_reader.hpp"
 
@@ -40,7 +38,6 @@ ChunksDownloadStrategy::GetChunk(RangeT const & range)
 
 void ChunksDownloadStrategy::InitChunks(int64_t fileSize, int64_t chunkSize, ChunkStatusT status)
 {
-  // init chunks which should be downloaded
   m_chunks.reserve(fileSize / chunkSize + 2);
   for (int64_t i = 0; i < fileSize; i += chunkSize)
     m_chunks.push_back(ChunkT(i, status));
@@ -70,7 +67,7 @@ void ChunksDownloadStrategy::SaveChunks(string const & fName)
   {
     try
     {
-      FileWriter w(fName + RESUME_FILE_EXTENSION);
+      FileWriter w(fName);
       w.Write(&m_chunks[0], sizeof(ChunkT) * m_chunks.size());
       return;
     }
@@ -81,7 +78,7 @@ void ChunksDownloadStrategy::SaveChunks(string const & fName)
   }
 
   // Delete if no chunks or some error occured.
-  (void)FileWriter::DeleteFileX(fName + RESUME_FILE_EXTENSION);
+  (void)FileWriter::DeleteFileX(fName);
 }
 
 int64_t ChunksDownloadStrategy::LoadOrInitChunks( string const & fName,
@@ -92,7 +89,7 @@ int64_t ChunksDownloadStrategy::LoadOrInitChunks( string const & fName,
 
   try
   {
-    FileReader r(fName + RESUME_FILE_EXTENSION);
+    FileReader r(fName);
 
     // Load chunks.
     size_t const count = r.Size() / sizeof(ChunkT);
@@ -106,7 +103,7 @@ int64_t ChunksDownloadStrategy::LoadOrInitChunks( string const & fName,
       if (m_chunks[i].m_status != CHUNK_COMPLETE)
         m_chunks[i].m_status = CHUNK_FREE;
       else
-        downloadedSize += m_chunks[i+1].m_pos - m_chunks[i].m_pos;
+        downloadedSize += (m_chunks[i+1].m_pos - m_chunks[i].m_pos);
     }
 
     return downloadedSize;
diff --git a/platform/chunks_download_strategy.hpp b/platform/chunks_download_strategy.hpp
index 2084c0e611..07a7fbefad 100644
--- a/platform/chunks_download_strategy.hpp
+++ b/platform/chunks_download_strategy.hpp
@@ -54,13 +54,17 @@ private:
 public:
   ChunksDownloadStrategy(vector<string> const & urls);
 
+  /// Init chunks vector for fileSize.
   void InitChunks(int64_t fileSize, int64_t chunkSize, ChunkStatusT status = CHUNK_FREE);
+
+  /// Used in unit tests only!
   void AddChunk(RangeT const & range, ChunkStatusT status);
 
   void SaveChunks(string const & fName);
   /// @return Already downloaded size.
   int64_t LoadOrInitChunks(string const & fName, int64_t fileSize, int64_t chunkSize);
 
+  /// Should be called for every completed chunk (no matter successful or not).
   void ChunkFinished(bool success, RangeT const & range);
 
   enum ResultT
diff --git a/platform/http_request.cpp b/platform/http_request.cpp
index 61c5ccff1c..2ce8fdb720 100644
--- a/platform/http_request.cpp
+++ b/platform/http_request.cpp
@@ -182,7 +182,7 @@ class FileHttpRequest : public HttpRequest, public IHttpThreadCallback
       // save information for download resume
       ++m_goodChunksCount;
       if (m_status != ECompleted && m_goodChunksCount % 10 == 0)
-        m_strategy.SaveChunks(m_filePath);
+        m_strategy.SaveChunks(m_filePath + RESUME_FILE_EXTENSION);
     }
 
     if (m_status != EInProgress)
@@ -195,12 +195,12 @@ class FileHttpRequest : public HttpRequest, public IHttpThreadCallback
         my::DeleteFileX(m_filePath + RESUME_FILE_EXTENSION);
 
         // Rename finished file to it's original name.
-        CHECK(my::RenameFileX((m_filePath + DOWNLOADING_FILE_EXTENSION).c_str(), m_filePath.c_str()), ());
+        CHECK(my::RenameFileX(m_filePath + DOWNLOADING_FILE_EXTENSION, m_filePath), ());
 
-        DisableBackupForFile(m_filePath.c_str());
+        DisableBackupForFile(m_filePath);
       }
       else // or save "chunks left" otherwise
-        m_strategy.SaveChunks(m_filePath);
+        m_strategy.SaveChunks(m_filePath + RESUME_FILE_EXTENSION);
 
       m_onFinish(*this);
     }
@@ -216,7 +216,8 @@ public:
   {
     ASSERT ( !urls.empty(), () );
 
-    m_progress.first = m_strategy.LoadOrInitChunks(m_filePath, fileSize, chunkSize);
+    m_progress.first = m_strategy.LoadOrInitChunks(m_filePath + RESUME_FILE_EXTENSION,
+                                                   fileSize, chunkSize);
     m_progress.second = fileSize;
 
 #ifdef OMIM_OS_IPHONE
@@ -239,7 +240,7 @@ public:
 
       if (m_doCleanProgressFiles)
       {
-        CHECK(my::DeleteFileX(m_filePath + DOWNLOADING_FILE_EXTENSION), ());
+        my::DeleteFileX(m_filePath + DOWNLOADING_FILE_EXTENSION);
         my::DeleteFileX(m_filePath + RESUME_FILE_EXTENSION);
       }
     }