--- a/doc/manual/source/attributes.rst	
+++ a/doc/manual/source/attributes.rst	
@@ -492,6 +492,10 @@ 
       // continue on with constructor.
     }
 
+Beware that the object must also implement a 
+``virtual TypeId GetInstanceTypeId (void) const;`` method. Either the
+``ObjectBase::ConstructSelf ()`` will not be able to read the attributes.
+
 Extending attributes
 ********************
 
--- a/src/internet/model/rtt-estimator.cc	
+++ a/src/internet/model/rtt-estimator.cc	
@@ -134,6 +134,12 @@ 
   NS_LOG_FUNCTION (this);
 }
 
+TypeId
+RttEstimator::GetInstanceTypeId (void) const
+{
+  return GetTypeId ();
+}
+
 void RttEstimator::SentSeq (SequenceNumber32 seq, uint32_t size)
 { 
   NS_LOG_FUNCTION (this << seq << size);
--- a/src/internet/model/rtt-estimator.h	
+++ a/src/internet/model/rtt-estimator.h	
@@ -64,6 +64,8 @@ 
 
   virtual ~RttEstimator();
 
+  virtual TypeId GetInstanceTypeId (void) const;
+
   /**
    * \brief Note that a particular sequence has been sent
    * \param seq the packet sequence number.