diff --git a/bg_helpers.cpp b/bg_helpers.cpp
index 6a4e3ff06..7daa91688 100644
--- a/bg_helpers.cpp
+++ b/bg_helpers.cpp
@@ -31,6 +31,21 @@ multi_polygon_type_fp buffer(multi_polygon_type_fp const & geometry_in, coordina
   }
 }
 
+multi_polygon_type_fp buffer_miter(multi_polygon_type_fp const & geometry_in, coordinate_type_fp expand_by) {
+  if (expand_by == 0) {
+    return geometry_in;
+  } else {
+    multi_polygon_type_fp geometry_out;
+    bg::buffer(geometry_in, geometry_out,
+               bg::strategy::buffer::distance_symmetric<coordinate_type_fp>(expand_by),
+               bg::strategy::buffer::side_straight(),
+               bg::strategy::buffer::join_miter(expand_by),
+               bg::strategy::buffer::end_round(points_per_circle),
+               bg::strategy::buffer::point_circle(points_per_circle));
+    return geometry_out;
+  }
+}
+
 template<typename CoordinateType>
 multi_polygon_type_fp buffer(polygon_type_fp const & geometry_in, CoordinateType expand_by) {
   return buffer(multi_polygon_type_fp{geometry_in}, expand_by);
@@ -38,6 +53,11 @@ multi_polygon_type_fp buffer(polygon_type_fp const & geometry_in, CoordinateType
 
 template multi_polygon_type_fp buffer(polygon_type_fp const&, double);
 
+template<typename CoordinateType>
+multi_polygon_type_fp buffer_miter(polygon_type_fp const & geometry_in, CoordinateType expand_by) {
+  return buffer_miter(multi_polygon_type_fp{geometry_in}, expand_by);
+}
+
 template<typename CoordinateType>
 multi_polygon_type_fp buffer(linestring_type_fp const & geometry_in, CoordinateType expand_by) {
   if (expand_by == 0) {
@@ -99,4 +119,11 @@ multi_polygon_type_fp buffer(ring_type_fp const & geometry_in, CoordinateType ex
 
 template multi_polygon_type_fp buffer(ring_type_fp const&, double);
 
+template<typename CoordinateType>
+multi_polygon_type_fp buffer_miter(ring_type_fp const & geometry_in, CoordinateType expand_by) {
+  return buffer_miter(polygon_type_fp{geometry_in}, expand_by);
+}
+
+template multi_polygon_type_fp buffer_miter(ring_type_fp const&, double);
+
 } // namespace bg_helpers
diff --git a/bg_helpers.hpp b/bg_helpers.hpp
index 7c313d941..f01b5350c 100644
--- a/bg_helpers.hpp
+++ b/bg_helpers.hpp
@@ -18,6 +18,8 @@ namespace bg_helpers {
 // 0, unlike bg::buffer.
 multi_polygon_type_fp buffer(multi_polygon_type_fp const & geometry_in, coordinate_type_fp expand_by);
 
+multi_polygon_type_fp buffer_miter(multi_polygon_type_fp const & geometry_in, coordinate_type_fp expand_by);
+
 template<typename CoordinateType>
 multi_polygon_type_fp buffer(polygon_type_fp const & geometry_in, CoordinateType expand_by);
 
@@ -27,6 +29,9 @@ multi_polygon_type_fp buffer(multi_linestring_type_fp const & geometry_in, Coord
 template<typename CoordinateType>
 multi_polygon_type_fp buffer(ring_type_fp const & geometry_in, CoordinateType expand_by);
 
+template<typename CoordinateType>
+multi_polygon_type_fp buffer_miter(ring_type_fp const & geometry_in, CoordinateType expand_by);
+
 } // namespace bg_helpers
 
 #endif //BG_HELPERS_HPP
diff --git a/path_finding.cpp b/path_finding.cpp
index 07808758b..eefaf9ea6 100644
--- a/path_finding.cpp
+++ b/path_finding.cpp
@@ -60,7 +60,7 @@ class PathFindingSurface {
                       }),
         all_vertices.end());
 
-    total_keep_in_grown = bg_helpers::buffer(total_keep_in, tolerance);
+    total_keep_in_grown = bg_helpers::buffer_miter(total_keep_in, tolerance);
   }
   multi_polygon_type_fp total_keep_in_grown;
   vector<point_type_fp> all_vertices;
diff --git a/surface_vectorial.cpp b/surface_vectorial.cpp
index a27125c88..494faaddb 100644
--- a/surface_vectorial.cpp
+++ b/surface_vectorial.cpp
@@ -166,7 +166,7 @@ vector<polygon_type_fp> find_thermal_reliefs(const multi_polygon_type_fp& millin
       auto thermal_hole = inner;
       bg::correct(thermal_hole); // Convert it from a hole to a filled-in shape.
       multi_polygon_type_fp shrunk_thermal_hole = 
-          bg_helpers::buffer(thermal_hole, -tolerance);
+          bg_helpers::buffer_miter(thermal_hole, -tolerance);
       bool empty_hole = !bg::intersects(shrunk_thermal_hole, milling_surface);
       if (!empty_hole) {
         continue;