diff --git a/src/libslic3r/ClipperUtils.cpp b/src/libslic3r/ClipperUtils.cpp
index 3df287f1d..8a4dfc03c 100644
--- a/src/libslic3r/ClipperUtils.cpp
+++ b/src/libslic3r/ClipperUtils.cpp
@@ -487,7 +487,7 @@ Slic3r::Polygons union_(const Slic3r::Polygons &subject, const Slic3r::Polygons
     { return _clipper(ClipperLib::ctUnion, ClipperUtils::PolygonsProvider(subject), ClipperUtils::PolygonsProvider(subject2), ApplySafetyOffset::No); }
 
 template <typename TSubject, typename TClip>
-static ExPolygons _clipper_ex(ClipperLib::ClipType clipType, TSubject &&subject,  TClip &&clip, ApplySafetyOffset do_safety_offset, ClipperLib::PolyFillType fill_type = ClipperLib::pftPositive)
+static ExPolygons _clipper_ex(ClipperLib::ClipType clipType, TSubject &&subject,  TClip &&clip, ApplySafetyOffset do_safety_offset, ClipperLib::PolyFillType fill_type = ClipperLib::pftNonZero)
     { return PolyTreeToExPolygons(_clipper_do_polytree2(clipType, std::forward<TSubject>(subject), std::forward<TClip>(clip), fill_type, do_safety_offset)); }
 
 Slic3r::ExPolygons diff_ex(const Slic3r::Polygons &subject, const Slic3r::Polygons &clip, ApplySafetyOffset do_safety_offset)
diff --git a/src/libslic3r/ClipperUtils.hpp b/src/libslic3r/ClipperUtils.hpp
index aa606e7c0..c4e014a74 100644
--- a/src/libslic3r/ClipperUtils.hpp
+++ b/src/libslic3r/ClipperUtils.hpp
@@ -357,7 +357,7 @@ Slic3r::Polygons union_(const Slic3r::Polygons &subject);
 Slic3r::Polygons union_(const Slic3r::ExPolygons &subject);
 Slic3r::Polygons union_(const Slic3r::Polygons &subject, const Slic3r::Polygons &subject2);
 // May be used to "heal" unusual models (3DLabPrints etc.) by providing fill_type (pftEvenOdd, pftNonZero, pftPositive, pftNegative).
-Slic3r::ExPolygons union_ex(const Slic3r::Polygons &subject, ClipperLib::PolyFillType fill_type = ClipperLib::pftPositive);
+Slic3r::ExPolygons union_ex(const Slic3r::Polygons &subject, ClipperLib::PolyFillType fill_type = ClipperLib::pftNonZero);
 Slic3r::ExPolygons union_ex(const Slic3r::ExPolygons &subject);
 Slic3r::ExPolygons union_ex(const Slic3r::Surfaces &subject);
 
diff --git a/src/libslic3r/PrintConfig.hpp b/src/libslic3r/PrintConfig.hpp
index 25c8f8abf..f2b9901d6 100644
--- a/src/libslic3r/PrintConfig.hpp
+++ b/src/libslic3r/PrintConfig.hpp
@@ -71,7 +71,7 @@ enum class IroningType {
 
 enum class SlicingMode
 {
-    // Regular, applying ClipperLib::pftPositive rule when creating ExPolygons.
+    // Regular, applying ClipperLib::pftNonZero rule when creating ExPolygons.
     Regular,
     // Compatible with 3DLabPrint models, applying ClipperLib::pftEvenOdd rule when creating ExPolygons.
     EvenOdd,
diff --git a/src/libslic3r/TriangleMeshSlicer.cpp b/src/libslic3r/TriangleMeshSlicer.cpp
index d08696ab3..f8b7d97c4 100644
--- a/src/libslic3r/TriangleMeshSlicer.cpp
+++ b/src/libslic3r/TriangleMeshSlicer.cpp
@@ -1179,7 +1179,7 @@ std::vector<ExPolygons> slice_mesh_ex(
                 Slic3r::make_expolygons(
                     layers_p[layer_id], params.closing_radius, params.extra_offset,
                     this_mode == MeshSlicingParams::SlicingMode::EvenOdd ? ClipperLib::pftEvenOdd : 
-                    this_mode == MeshSlicingParams::SlicingMode::PositiveLargestContour ? ClipperLib::pftNonZero : ClipperLib::pftPositive,
+                    this_mode == MeshSlicingParams::SlicingMode::PositiveLargestContour ? ClipperLib::pftPositive : ClipperLib::pftNonZero,
                     &expolygons);
                 //FIXME simplify
                 if (this_mode == MeshSlicingParams::SlicingMode::PositiveLargestContour)
diff --git a/src/libslic3r/TriangleMeshSlicer.hpp b/src/libslic3r/TriangleMeshSlicer.hpp
index 344b42416..ad0fd42da 100644
--- a/src/libslic3r/TriangleMeshSlicer.hpp
+++ b/src/libslic3r/TriangleMeshSlicer.hpp
@@ -12,13 +12,13 @@ struct MeshSlicingParams
 {
     enum class SlicingMode : uint32_t {
         // Regular slicing, maintain all contours and their orientation.
-        // slice_mesh_ex() applies ClipperLib::pftPositive rule to the result of slice_mesh().
+        // slice_mesh_ex() applies ClipperLib::pftNonZero rule to the result of slice_mesh().
         Regular,
         // For slicing 3DLabPrints plane models (aka to be compatible with S3D default strategy).
         // slice_mesh_ex() applies ClipperLib::pftEvenOdd rule. slice_mesh() slices EvenOdd as Regular.
         EvenOdd,
         // Maintain all contours, orient all contours CCW.
-        // slice_mesh_ex() applies ClipperLib::pftPositive rule, thus holes will be closed.
+        // slice_mesh_ex() applies ClipperLib::pftNonZero rule, thus holes will be closed.
         Positive,
         // Orient all contours CCW and keep only the contour with the largest area.
         // This mode is useful for slicing complex objects in vase mode.