diff --git a/kmeans.hpp b/kmeans.hpp
index 01727ab5..a7d691fd 100644
--- a/kmeans.hpp
+++ b/kmeans.hpp
@@ -75,7 +75,7 @@ namespace util {
             std::forward<InputT>  (src),
             std::forward<OutputT> (dst),
             [] (auto a, auto b) {
-                return distance (a, b);
+                return norm (a - b);
         });
     }