--- boost_1_49_0/tools/quickbook/src/intrusive_base.hpp.orig	2012-04-14 00:26:49.360818878 -0700
+++ boost_1_49_0/tools/quickbook/src/intrusive_base.hpp	2012-04-14 00:27:10.214279871 -0700
@@ -21,7 +21,7 @@
         intrusive_base() : ref_count_(0) {}
         intrusive_base(intrusive_base const&) : ref_count_(0) {}
         intrusive_base& operator=(intrusive_base const&) { return *this; }
-        ~intrusive_base() { assert(!ref_count_); }
+        virtual ~intrusive_base() { assert(!ref_count_); }
 
         friend void intrusive_ptr_add_ref(T* ptr)
             { ++ptr->ref_count_; }