diff --git a/src/hash.h b/src/hash.h
index 88926ab31..73e31580d 100644
--- a/src/hash.h
+++ b/src/hash.h
@@ -132,9 +132,9 @@ class CHashWriter
 private:
     CHash256 ctx;
 
+    const int nType;
+    const int nVersion;
 public:
-    int nType;
-    int nVersion;
 
     CHashWriter(int nTypeIn, int nVersionIn) : nType(nTypeIn), nVersion(nVersionIn) {}
 
diff --git a/src/net.h b/src/net.h
index 22b80fc50..4ceeec2f0 100644
--- a/src/net.h
+++ b/src/net.h
@@ -140,7 +140,7 @@ public:
     void PushMessageWithVersionAndFlag(CNode* pnode, int nVersion, int flag, const std::string& sCommand, Args&&... args)
     {
         auto msg(BeginMessage(pnode, nVersion, flag, sCommand));
-        ::SerializeMany(msg, msg.nType, msg.nVersion, std::forward<Args>(args)...);
+        ::SerializeMany(msg, msg.GetType(), msg.GetVersion(), std::forward<Args>(args)...);
         EndMessage(msg);
         PushMessage(pnode, msg, sCommand);
     }
diff --git a/src/serialize.h b/src/serialize.h
index f8e82edf8..68a8e2847 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -937,9 +937,9 @@ class CSizeComputer
 protected:
     size_t nSize;
 
+    const int nType;
+    const int nVersion;
 public:
-    int nType;
-    int nVersion;
 
     CSizeComputer(int nTypeIn, int nVersionIn) : nSize(0), nType(nTypeIn), nVersion(nVersionIn) {}
 
diff --git a/src/streams.h b/src/streams.h
index 582443ab4..12a36a4a7 100644
--- a/src/streams.h
+++ b/src/streams.h
@@ -26,10 +26,11 @@ template<typename Stream>
 class OverrideStream
 {
     Stream* stream;
-public:
+
     const int nType;
     const int nVersion;
 
+public:
     OverrideStream(Stream* stream_, int nType_, int nVersion_) : stream(stream_), nType(nType_), nVersion(nVersion_) {}
 
     template<typename T>
@@ -66,9 +67,10 @@ protected:
     typedef CSerializeData vector_type;
     vector_type vch;
     unsigned int nReadPos;
-public:
+
     int nType;
     int nVersion;
+public:
 
     typedef vector_type::allocator_type   allocator_type;
     typedef vector_type::size_type        size_type;
@@ -251,9 +253,9 @@ public:
     int in_avail()               { return size(); }
 
     void SetType(int n)          { nType = n; }
-    int GetType()                { return nType; }
+    int GetType() const          { return nType; }
     void SetVersion(int n)       { nVersion = n; }
-    int GetVersion()             { return nVersion; }
+    int GetVersion() const       { return nVersion; }
 
     void read(char* pch, size_t nSize)
     {
@@ -380,17 +382,15 @@ private:
     CAutoFile(const CAutoFile&);
     CAutoFile& operator=(const CAutoFile&);
 
-    int nType;
-    int nVersion;
-	
+    const int nType;
+    const int nVersion;
+
     FILE* file;	
 
 public:
-    CAutoFile(FILE* filenew, int nTypeIn, int nVersionIn)
+    CAutoFile(FILE* filenew, int nTypeIn, int nVersionIn) : nType(nTypeIn), nVersion(nVersionIn)
     {
         file = filenew;
-        nType = nTypeIn;
-        nVersion = nVersionIn;
     }
 
     ~CAutoFile()
@@ -425,10 +425,8 @@ public:
     //
     // Stream subset
     //
-    void SetType(int n)          { nType = n; }
-    int GetType()                { return nType; }
-    void SetVersion(int n)       { nVersion = n; }
-    int GetVersion()             { return nVersion; }
+    int GetType() const          { return nType; }
+    int GetVersion() const       { return nVersion; }
 
     void read(char* pch, size_t nSize)
     {
@@ -500,8 +498,8 @@ private:
     CBufferedFile(const CBufferedFile&);
     CBufferedFile& operator=(const CBufferedFile&);
 
-    int nType;
-    int nVersion;
+    const int nType;
+    const int nVersion;
 
     FILE *src;            // source file
     uint64_t nSrcPos;     // how many bytes have been read from source
@@ -531,11 +529,9 @@ protected:
 
 public:
     CBufferedFile(FILE *fileIn, uint64_t nBufSize, uint64_t nRewindIn, int nTypeIn, int nVersionIn) :
-        nSrcPos(0), nReadPos(0), nReadLimit((uint64_t)(-1)), nRewind(nRewindIn), vchBuf(nBufSize, 0)
+        nType(nTypeIn), nVersion(nVersionIn), nSrcPos(0), nReadPos(0), nReadLimit((uint64_t)(-1)), nRewind(nRewindIn), vchBuf(nBufSize, 0)
     {
         src = fileIn;
-        nType = nTypeIn;
-        nVersion = nVersionIn;
     }
 
     ~CBufferedFile()