diff --git a/src/encoder.hpp b/src/encoder.hpp
index 93b654bd..aac27515 100644
--- a/src/encoder.hpp
+++ b/src/encoder.hpp
@@ -54,14 +54,14 @@ namespace zmq
 template <typename T> class encoder_base_t : public i_encoder
 {
   public:
-    inline encoder_base_t (size_t bufsize_) :
+    inline explicit encoder_base_t (size_t bufsize_) :
         _write_pos (0),
         _to_write (0),
         _next (NULL),
         _new_msg_flag (false),
         _buf_size (bufsize_),
         _buf (static_cast<unsigned char *> (malloc (bufsize_))),
-        in_progress (NULL)
+        _in_progress (NULL)
     {
         alloc_assert (_buf);
     }
@@ -78,7 +78,7 @@ template <typename T> class encoder_base_t : public i_encoder
         unsigned char *buffer = !*data_ ? _buf : *data_;
         size_t buffersize = !*data_ ? _buf_size : size_;
 
-        if (in_progress == NULL)
+        if (in_progress () == NULL)
             return 0;
 
         size_t pos = 0;
@@ -88,11 +88,11 @@ template <typename T> class encoder_base_t : public i_encoder
             //  in the buffer.
             if (!_to_write) {
                 if (_new_msg_flag) {
-                    int rc = in_progress->close ();
+                    int rc = _in_progress->close ();
                     errno_assert (rc == 0);
-                    rc = in_progress->init ();
+                    rc = _in_progress->init ();
                     errno_assert (rc == 0);
-                    in_progress = NULL;
+                    _in_progress = NULL;
                     break;
                 }
                 (static_cast<T *> (this)->*_next) ();
@@ -130,8 +130,8 @@ template <typename T> class encoder_base_t : public i_encoder
 
     void load_msg (msg_t *msg_)
     {
-        zmq_assert (in_progress == NULL);
-        in_progress = msg_;
+        zmq_assert (in_progress () == NULL);
+        _in_progress = msg_;
         (static_cast<T *> (this)->*_next) ();
     }
 
@@ -152,6 +152,8 @@ template <typename T> class encoder_base_t : public i_encoder
         _new_msg_flag = new_msg_flag_;
     }
 
+    msg_t *in_progress () { return _in_progress; }
+
   private:
     //  Where to get the data to write from.
     unsigned char *_write_pos;
@@ -172,8 +174,7 @@ template <typename T> class encoder_base_t : public i_encoder
     encoder_base_t (const encoder_base_t &);
     void operator= (const encoder_base_t &);
 
-  protected:
-    msg_t *in_progress;
+    msg_t *_in_progress;
 };
 }
 
diff --git a/src/raw_encoder.cpp b/src/raw_encoder.cpp
index fa510963..39c7633e 100644
--- a/src/raw_encoder.cpp
+++ b/src/raw_encoder.cpp
@@ -45,6 +45,6 @@ zmq::raw_encoder_t::~raw_encoder_t ()
 
 void zmq::raw_encoder_t::raw_message_ready ()
 {
-    next_step (in_progress->data (), in_progress->size (),
+    next_step (in_progress ()->data (), in_progress ()->size (),
                &raw_encoder_t::raw_message_ready, true);
 }
diff --git a/src/v1_encoder.cpp b/src/v1_encoder.cpp
index cc78d417..8ef22ae7 100644
--- a/src/v1_encoder.cpp
+++ b/src/v1_encoder.cpp
@@ -49,14 +49,14 @@ zmq::v1_encoder_t::~v1_encoder_t ()
 void zmq::v1_encoder_t::size_ready ()
 {
     //  Write message body into the buffer.
-    next_step (in_progress->data (), in_progress->size (),
+    next_step (in_progress ()->data (), in_progress ()->size (),
                &v1_encoder_t::message_ready, true);
 }
 
 void zmq::v1_encoder_t::message_ready ()
 {
     //  Get the message size.
-    size_t size = in_progress->size ();
+    size_t size = in_progress ()->size ();
 
     //  Account for the 'flags' byte.
     size++;
@@ -66,12 +66,12 @@ void zmq::v1_encoder_t::message_ready ()
     //  message size. In both cases 'flags' field follows.
     if (size < UCHAR_MAX) {
         _tmpbuf[0] = static_cast<unsigned char> (size);
-        _tmpbuf[1] = (in_progress->flags () & msg_t::more);
+        _tmpbuf[1] = (in_progress ()->flags () & msg_t::more);
         next_step (_tmpbuf, 2, &v1_encoder_t::size_ready, false);
     } else {
         _tmpbuf[0] = UCHAR_MAX;
         put_uint64 (_tmpbuf + 1, size);
-        _tmpbuf[9] = (in_progress->flags () & msg_t::more);
+        _tmpbuf[9] = (in_progress ()->flags () & msg_t::more);
         next_step (_tmpbuf, 10, &v1_encoder_t::size_ready, false);
     }
 }
diff --git a/src/v2_encoder.cpp b/src/v2_encoder.cpp
index 1a869068..88f005a9 100644
--- a/src/v2_encoder.cpp
+++ b/src/v2_encoder.cpp
@@ -52,17 +52,17 @@ void zmq::v2_encoder_t::message_ready ()
     //  Encode flags.
     unsigned char &protocol_flags = _tmp_buf[0];
     protocol_flags = 0;
-    if (in_progress->flags () & msg_t::more)
+    if (in_progress ()->flags () & msg_t::more)
         protocol_flags |= v2_protocol_t::more_flag;
-    if (in_progress->size () > UCHAR_MAX)
+    if (in_progress ()->size () > UCHAR_MAX)
         protocol_flags |= v2_protocol_t::large_flag;
-    if (in_progress->flags () & msg_t::command)
+    if (in_progress ()->flags () & msg_t::command)
         protocol_flags |= v2_protocol_t::command_flag;
 
     //  Encode the message length. For messages less then 256 bytes,
     //  the length is encoded as 8-bit unsigned integer. For larger
     //  messages, 64-bit unsigned integer in network byte order is used.
-    const size_t size = in_progress->size ();
+    const size_t size = in_progress ()->size ();
     if (unlikely (size > UCHAR_MAX)) {
         put_uint64 (_tmp_buf + 1, size);
         next_step (_tmp_buf, 9, &v2_encoder_t::size_ready, false);
@@ -75,6 +75,6 @@ void zmq::v2_encoder_t::message_ready ()
 void zmq::v2_encoder_t::size_ready ()
 {
     //  Write message body into the buffer.
-    next_step (in_progress->data (), in_progress->size (),
+    next_step (in_progress ()->data (), in_progress ()->size (),
                &v2_encoder_t::message_ready, true);
 }