diff --git a/src/libslic3r/VariableWidth.cpp b/src/libslic3r/VariableWidth.cpp
index 6f7407d70..e01050e4a 100644
--- a/src/libslic3r/VariableWidth.cpp
+++ b/src/libslic3r/VariableWidth.cpp
@@ -123,11 +123,11 @@ static ExtrusionPaths thick_polyline_to_extrusion_paths_2(const ThickPolyline& t
             if (start_index != i){
                 path = ExtrusionPath(role);
                 double length = lines[start_index].length();
-                double sum = lines[start_index].length() * lines[start_index].a_width;
+                double sum = lines[start_index].length() * 0.5 * (lines[start_index].a_width + lines[start_index].b_width);
                 path.polyline.append(lines[start_index].a);
                 for (int idx = start_index + 1; idx < i; idx++) {
                     length += lines[idx].length();
-                    sum += lines[idx].length() * lines[idx].a_width;
+                    sum += lines[idx].length() * 0.5 * (lines[idx].a_width + lines[idx].b_width);
                     path.polyline.append(lines[idx].a);
                 }
                 path.polyline.append(lines[i].a);