diff --git a/include/boost/geometry/algorithms/detail/buffer/parallel_continue.hpp b/include/boost/geometry/algorithms/detail/buffer/parallel_continue.hpp
index be9d2cfad..119d64de7 100644
--- a/include/boost/geometry/algorithms/detail/buffer/parallel_continue.hpp
+++ b/include/boost/geometry/algorithms/detail/buffer/parallel_continue.hpp
@@ -9,8 +9,6 @@
 #ifndef BOOST_GEOMETRY_ALGORITHMS_DETAIL_BUFFER_PARALLEL_CONTINUE_HPP
 #define BOOST_GEOMETRY_ALGORITHMS_DETAIL_BUFFER_PARALLEL_CONTINUE_HPP
 
-#include <boost/geometry/util/math.hpp>
-
 
 namespace boost { namespace geometry
 {
@@ -22,8 +20,8 @@ namespace detail { namespace buffer
 template <typename T>
 inline bool parallel_continue(T dx1, T dy1, T dx2, T dy2)
 {
-    return math::sign(dx1) == math::sign(dx2)
-        && math::sign(dy1) == math::sign(dy2);
+    T const dot = dx1 * dx2 + dy1 * dy2;
+    return dot > 0;
 }
 
 }} // namespace detail::buffer