diff --git a/enable_shared_from_this_test.cpp b/enable_shared_from_this_test.cpp
index 66f9c17..8225a39 100644
--- a/enable_shared_from_this_test.cpp
+++ b/enable_shared_from_this_test.cpp
@@ -72,7 +72,10 @@ int main()
     return boost::report_errors();
 }
 
-class impl: public X, public Y, public boost::enable_shared_from_this<impl>
+// virtual inheritance from Y to stress the implementation
+// (prevents Y* -> impl* casts)
+
+class impl: public X, public virtual Y, public boost::enable_shared_from_this<impl>
 {
 public:
 
@@ -88,8 +91,14 @@ public:
     }
 };
 
+// intermediate impl2 to stress the implementation
+
+class impl2: public impl
+{
+};
+
 boost::shared_ptr<Y> createY()
 {
-    boost::shared_ptr<impl> pi(new impl);
+    boost::shared_ptr<Y> pi(new impl2);
     return pi;
 }
diff --git a/include/boost/enable_shared_from_this.hpp b/include/boost/enable_shared_from_this.hpp
index ae5d809..4dfdab6 100644
--- a/include/boost/enable_shared_from_this.hpp
+++ b/include/boost/enable_shared_from_this.hpp
@@ -28,28 +28,20 @@ public:
 
     shared_ptr<T> shared_from_this()
     {
-        shared_ptr<T> p(weak_this);
+        shared_ptr<T> p(_internal_weak_this);
         BOOST_ASSERT(p.get() == this);
         return p;
     }
 
     shared_ptr<T const> shared_from_this() const
     {
-        shared_ptr<T const> p(weak_this);
+        shared_ptr<T const> p(_internal_weak_this);
         BOOST_ASSERT(p.get() == this);
         return p;
     }
 
-#ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
-
-private:
-
-    template<class Y> friend class shared_ptr;
-
-#endif
-
-    typedef T element_type; // for bcc 5.5.1
-    weak_ptr<element_type> weak_this;
+    typedef T _internal_element_type; // for bcc 5.5.1
+    weak_ptr<_internal_element_type> _internal_weak_this;
 };
 
 } // namespace boost
diff --git a/include/boost/shared_ptr.hpp b/include/boost/shared_ptr.hpp
index b03a391..8fc45ea 100644
--- a/include/boost/shared_ptr.hpp
+++ b/include/boost/shared_ptr.hpp
@@ -39,6 +39,9 @@
 namespace boost
 {
 
+template<class T> class weak_ptr;
+template<class T> class enable_shared_from_this;
+
 namespace detail
 {
 
@@ -65,6 +68,17 @@ template<> struct shared_ptr_traits<void const>
 
 #endif
 
+// enable_shared_from_this support
+
+template<class T, class Y> void sp_enable_shared_from_this(boost::enable_shared_from_this<T> * pe, Y * px, shared_count const & pn)
+{
+    pe->_internal_weak_this._internal_assign(px, pn);
+}
+
+void sp_enable_shared_from_this(void const *, void const *, shared_count const &)
+{
+}
+
 } // namespace detail
 
 
@@ -76,9 +90,6 @@ template<> struct shared_ptr_traits<void const>
 //  is destroyed or reset.
 //
 
-template<class T> class weak_ptr;
-template<class T> class enable_shared_from_this;
-
 template<class T> class shared_ptr
 {
 private:
@@ -86,17 +97,6 @@ private:
     // Borland 5.5.1 specific workaround
     typedef shared_ptr<T> this_type;
 
-    // enable_shared_from_this support
-
-    template<class Y> void sp_enable_shared_from_this(boost::enable_shared_from_this<Y> * q)
-    {
-        q->weak_this = *this;
-    }
-
-    void sp_enable_shared_from_this(void *)
-    {
-    }
-
 public:
 
     typedef T element_type;
@@ -111,7 +111,7 @@ public:
     template<class Y>
     explicit shared_ptr(Y * p): px(p), pn(p, checked_deleter<Y>()) // Y must be complete
     {
-        sp_enable_shared_from_this(p);
+        detail::sp_enable_shared_from_this(p, p, pn);
     }
 
     //
@@ -122,7 +122,7 @@ public:
 
     template<class Y, class D> shared_ptr(Y * p, D d): px(p), pn(p, d)
     {
-        sp_enable_shared_from_this(p);
+        detail::sp_enable_shared_from_this(p, p, pn);
     }
 
 //  generated copy constructor, assignment, destructor are fine...
@@ -179,7 +179,7 @@ public:
     {
         Y * tmp = r.get();
         pn = detail::shared_count(r);
-        sp_enable_shared_from_this(tmp);
+        detail::sp_enable_shared_from_this(tmp, tmp, pn);
     }
 
 #endif
@@ -270,7 +270,7 @@ public:
         pn.swap(other.pn);
     }
 
-    bool less(this_type const & rhs) const // implementation detail, never throws
+    bool _internal_less(this_type const & rhs) const // implementation detail, never throws
     {
         return pn < rhs.pn;
     }
@@ -316,7 +316,7 @@ template<class T> inline bool operator!=(shared_ptr<T> const & a, shared_ptr<T>
 
 template<class T> inline bool operator<(shared_ptr<T> const & a, shared_ptr<T> const & b)
 {
-    return a.less(b);
+    return a._internal_less(b);
 }
 
 template<class T> inline void swap(shared_ptr<T> & a, shared_ptr<T> & b)
diff --git a/include/boost/weak_ptr.hpp b/include/boost/weak_ptr.hpp
index b65309e..a4154ea 100644
--- a/include/boost/weak_ptr.hpp
+++ b/include/boost/weak_ptr.hpp
@@ -92,7 +92,13 @@ public:
         pn.swap(other.pn);
     }
 
-    bool less(this_type const & rhs) const // implementation detail, never throws
+    void _internal_assign(T * px2, detail::shared_count const & pn2) // implementation detail
+    {
+        px = px2;
+        pn = pn2;
+    }
+
+    bool _internal_less(this_type const & rhs) const // implementation detail, never throws
     {
         return pn < rhs.pn;
     }
@@ -116,7 +122,7 @@ private:
 
 template<class T> inline bool operator<(weak_ptr<T> const & a, weak_ptr<T> const & b)
 {
-    return a.less(b);
+    return a._internal_less(b);
 }
 
 template<class T> void swap(weak_ptr<T> & a, weak_ptr<T> & b)