diff --git a/include/boost/range/iterator_range_core.hpp b/include/boost/range/iterator_range_core.hpp
index 497b1e3..5d809f1 100755
--- a/include/boost/range/iterator_range_core.hpp
+++ b/include/boost/range/iterator_range_core.hpp
@@ -230,7 +230,7 @@ namespace boost
 
             difference_type size() const
             {
-                return m_End - m_Begin;
+                return std::distance(m_End, m_Begin);
             }
 
             bool empty() const