diff --git a/src/slic3r/GUI/GLGizmo.cpp b/src/slic3r/GUI/GLGizmo.cpp
index a7953572e..9decc625d 100644
--- a/src/slic3r/GUI/GLGizmo.cpp
+++ b/src/slic3r/GUI/GLGizmo.cpp
@@ -1559,7 +1559,7 @@ void GLGizmoFlatten::update_planes()
         while (facet_queue_cnt > 0) {
             int facet_idx = facet_queue[-- facet_queue_cnt];
             const stl_normal& this_normal = ch.stl.facet_start[facet_idx].normal;
-            if (this_normal.isApprox(*normal_ptr)) {
+            if (std::abs(this_normal(0) - (*normal_ptr)(0)) < 0.001 && std::abs(this_normal(1) - (*normal_ptr)(1)) < 0.001 && std::abs(this_normal(2) - (*normal_ptr)(2)) < 0.001) {
                 stl_vertex* first_vertex = ch.stl.facet_start[facet_idx].vertex;
                 for (int j=0; j<3; ++j)
                     m_planes.back().vertices.emplace_back((double)first_vertex[j](0), (double)first_vertex[j](1), (double)first_vertex[j](2));