diff --git a/include/boost/container/detail/is_contiguous_container.hpp b/include/boost/container/detail/is_contiguous_container.hpp
index 528aeee..47ab363 100644
--- a/include/boost/container/detail/is_contiguous_container.hpp
+++ b/include/boost/container/detail/is_contiguous_container.hpp
@@ -26,6 +26,14 @@
 #define BOOST_INTRUSIVE_HAS_MEMBER_FUNCTION_CALLABLE_WITH_MAX 0
 #include <boost/intrusive/detail/has_member_function_callable_with.hpp>
 
+//back_free_capacity
+#define BOOST_INTRUSIVE_HAS_MEMBER_FUNCTION_CALLABLE_WITH_FUNCNAME back_free_capacity
+#define BOOST_INTRUSIVE_HAS_MEMBER_FUNCTION_CALLABLE_WITH_NS_BEG namespace boost { namespace container { namespace back_free_capacity_detail {
+#define BOOST_INTRUSIVE_HAS_MEMBER_FUNCTION_CALLABLE_WITH_NS_END   }}}
+#define BOOST_INTRUSIVE_HAS_MEMBER_FUNCTION_CALLABLE_WITH_MIN 0
+#define BOOST_INTRUSIVE_HAS_MEMBER_FUNCTION_CALLABLE_WITH_MAX 0
+#include <boost/intrusive/detail/has_member_function_callable_with.hpp>
+
 namespace boost {
 namespace container {
 namespace dtl {
@@ -40,6 +48,23 @@ struct is_contiguous_container
          has_member_function_callable_with_data<const Container>::value;
 };
 
+
+template < class Container
+         , bool = boost::container::back_free_capacity_detail::
+                     has_member_function_callable_with_back_free_capacity<const Container>::value>
+struct back_free_capacity
+{
+   static typename Container::size_type get(const Container &c)
+   {  return c.back_free_capacity();  }
+};
+
+template < class Container>
+struct back_free_capacity<Container, false>
+{
+   static typename Container::size_type get(const Container &c)
+   {  return c.capacity() - c.size();  }
+};
+
 }  //namespace dtl {
 }  //namespace container {
 }  //namespace boost {