diff --git a/src/libslic3r/TriangleMeshSlicer.cpp b/src/libslic3r/TriangleMeshSlicer.cpp
index 3fd0da660..3cee8b0ac 100644
--- a/src/libslic3r/TriangleMeshSlicer.cpp
+++ b/src/libslic3r/TriangleMeshSlicer.cpp
@@ -332,16 +332,16 @@ void slice_facet_at_zs(
     // find facet extents
     const float min_z = fminf(vertices[0].z(), fminf(vertices[1].z(), vertices[2].z()));
     const float max_z = fmaxf(vertices[0].z(), fmaxf(vertices[1].z(), vertices[2].z()));
-    
+
     // find layer extents
     auto min_layer = std::lower_bound(zs.begin(), zs.end(), min_z); // first layer whose slice_z is >= min_z
     auto max_layer = std::upper_bound(min_layer, zs.end(), max_z); // first layer whose slice_z is > max_z
     int  idx_vertex_lowest = (vertices[1].z() == min_z) ? 1 : ((vertices[2].z() == min_z) ? 2 : 0);
-    
+
     for (auto it = min_layer; it != max_layer; ++ it) {
         IntersectionLine il;
         // Ignore horizontal triangles. Any valid horizontal triangle must have a vertical triangle connected, otherwise the part has zero volume.
-        if (min_z != max_z && slice_facet(*it, vertices, indices, edge_ids, idx_vertex_lowest, false, il) == FacetSliceType::Slicing) {
+        if (!is_equal(min_z , max_z) && slice_facet(*it, vertices, indices, edge_ids, idx_vertex_lowest, false, il) == FacetSliceType::Slicing) {
             assert(il.edge_type != IntersectionLine::FacetEdgeType::Horizontal);
             size_t slice_id = it - zs.begin();
             boost::lock_guard<std::mutex> l(lines_mutex[slice_id % lines_mutex.size()]);
@@ -392,10 +392,10 @@ static inline IntersectionLines slice_make_lines(
             const float min_z = fminf(vertices[0].z(), fminf(vertices[1].z(), vertices[2].z()));
             const float max_z = fmaxf(vertices[0].z(), fmaxf(vertices[1].z(), vertices[2].z()));
             assert(min_z <= plane_z && max_z >= plane_z);
-            int  idx_vertex_lowest = (vertices[1].z() == min_z) ? 1 : ((vertices[2].z() == min_z) ? 2 : 0);            
+            int  idx_vertex_lowest = (vertices[1].z() == min_z) ? 1 : ((vertices[2].z() == min_z) ? 2 : 0);
             IntersectionLine il;
             // Ignore horizontal triangles. Any valid horizontal triangle must have a vertical triangle connected, otherwise the part has zero volume.
-            if (min_z != max_z && slice_facet(plane_z, vertices, indices, face_edge_ids[face_idx], idx_vertex_lowest, false, il) == FacetSliceType::Slicing) {
+            if (!is_equal(min_z, max_z) && slice_facet(plane_z, vertices, indices, face_edge_ids[face_idx], idx_vertex_lowest, false, il) == FacetSliceType::Slicing) {
                 assert(il.edge_type != IntersectionLine::FacetEdgeType::Horizontal);
                 lines.emplace_back(il);
             }