diff --git a/include/boost/algorithm/cluster/cluster_data.hpp b/include/boost/algorithm/cluster/cluster_data.hpp
index c5186db..6e998fb 100644
--- a/include/boost/algorithm/cluster/cluster_data.hpp
+++ b/include/boost/algorithm/cluster/cluster_data.hpp
@@ -52,6 +52,7 @@ struct cluster_data
   value_type & back() { return m_pClusters->back(); }
   value_type const & back() const { return m_pClusters->back(); }
 
+  size_t size() const { return m_pClusters->size(); }
 private:
   boost::shared_ptr<clusters> m_pClusters;
 };
diff --git a/include/boost/algorithm/cluster/dbscan.hpp b/include/boost/algorithm/cluster/dbscan.hpp
index a7a9480..f0d8dcc 100644
--- a/include/boost/algorithm/cluster/dbscan.hpp
+++ b/include/boost/algorithm/cluster/dbscan.hpp
@@ -9,6 +9,7 @@
 #include <boost/algorithm/cluster/cluster_data.hpp>
 #include <boost/algorithm/cluster/concept.hpp>
 #include <boost/algorithm/cluster/detail/naive_query.hpp>
+#include <boost/utility/result_of.hpp>
 #include <vector>
 
 namespace boost
@@ -45,11 +46,12 @@ struct node
  * \param[in] d
  * \return The cluster data (partitioning of the tuples).
  */
-template<typename ClusterT, typename NTupleIterT, typename DistFunT>
+template<typename ClusterT, typename NTupleIterT,
+         typename DistanceT, typename DistFunT>
 cluster_data<ClusterT>
 dbscan(NTupleIterT const & begin,
        NTupleIterT const & end, 
-       typename NTupleIterT::difference_type const & eps,
+       DistanceT const & eps,
        size_t min_points,
        DistFunT const & d)
 {
@@ -57,6 +59,8 @@ dbscan(NTupleIterT const & begin,
   function_requires<
     DistanceComparableConcept<typename NTupleIterT::value_type, DistFunT> >();
     //DistanceComparableConcept<int, DistFunT> >();
+  function_requires<
+    DistanceComparableConcept<DistanceT, DistFunT> >();
 
   // TODO: Rework the algorithm to NOT make this extra collection?
   typedef detail::node<NTupleIterT> node;
diff --git a/include/boost/algorithm/cluster/detail/naive_query.hpp b/include/boost/algorithm/cluster/detail/naive_query.hpp
index 7ba780c..5a05409 100644
--- a/include/boost/algorithm/cluster/detail/naive_query.hpp
+++ b/include/boost/algorithm/cluster/detail/naive_query.hpp
@@ -21,12 +21,12 @@ namespace detail
 
 // TODO: Replace this naive query function w/ R*-tree or fractional cascading.
 // This query mechanism makes the runtime quadratic.
-template<typename NTupleIterT, typename DistFunT>
+template<typename NTupleIterT, typename DistanceT, typename DistFunT>
 static void naive_query(
   NTupleIterT const & query_pt,
   NTupleIterT const & begin,
   NTupleIterT const & end,
-  typename NTupleIterT::difference_type eps,
+  DistanceT const & eps,
   DistFunT const & d,
   std::vector<NTupleIterT> & v)
 {