diff --git a/lib/Slic3r/Layer/Region.pm b/lib/Slic3r/Layer/Region.pm
index edf56f243..f65e90129 100644
--- a/lib/Slic3r/Layer/Region.pm
+++ b/lib/Slic3r/Layer/Region.pm
@@ -53,30 +53,6 @@ sub make_perimeters {
     $generator->process;
 }
 
-sub prepare_fill_surfaces {
-    my $self = shift;
-    
-    # Note: in order to make the psPrepareInfill step idempotent, we should never
-    # alter fill_surfaces boundaries on which our idempotency relies since that's
-    # the only meaningful information returned by psPerimeters.
-    
-    # if no solid layers are requested, turn top/bottom surfaces to internal
-    if ($self->config->top_solid_layers == 0) {
-        $_->surface_type(S_TYPE_INTERNAL) for @{$self->fill_surfaces->filter_by_type(S_TYPE_TOP)};
-    }
-    if ($self->config->bottom_solid_layers == 0) {
-        $_->surface_type(S_TYPE_INTERNAL)
-            for @{$self->fill_surfaces->filter_by_type(S_TYPE_BOTTOM)}, @{$self->fill_surfaces->filter_by_type(S_TYPE_BOTTOMBRIDGE)};
-    }
-        
-    # turn too small internal regions into solid regions according to the user setting
-    if ($self->config->fill_density > 0) {
-        my $min_area = scale scale $self->config->solid_infill_below_area; # scaling an area requires two calls!
-        $_->surface_type(S_TYPE_INTERNALSOLID)
-            for grep { $_->area <= $min_area } @{$self->fill_surfaces->filter_by_type(S_TYPE_INTERNAL)};
-    }
-}
-
 sub process_external_surfaces {
     my ($self, $lower_layer) = @_;
     
diff --git a/xs/src/libslic3r/Layer.hpp b/xs/src/libslic3r/Layer.hpp
index c21ffa1c8..6dd6e81a5 100644
--- a/xs/src/libslic3r/Layer.hpp
+++ b/xs/src/libslic3r/Layer.hpp
@@ -56,6 +56,7 @@ class LayerRegion
     
     Flow flow(FlowRole role, bool bridge = false, double width = -1) const;
     void merge_slices();
+    void prepare_fill_surfaces();
     
     private:
     Layer *_layer;
diff --git a/xs/src/libslic3r/LayerRegion.cpp b/xs/src/libslic3r/LayerRegion.cpp
index 7b8e77f5a..e988566a8 100644
--- a/xs/src/libslic3r/LayerRegion.cpp
+++ b/xs/src/libslic3r/LayerRegion.cpp
@@ -53,6 +53,38 @@ LayerRegion::merge_slices()
         this->slices.surfaces.push_back(Surface(stInternal, *expoly));
 }
 
+void
+LayerRegion::prepare_fill_surfaces()
+{
+    /*  Note: in order to make the psPrepareInfill step idempotent, we should never
+        alter fill_surfaces boundaries on which our idempotency relies since that's
+        the only meaningful information returned by psPerimeters. */
+    
+    // if no solid layers are requested, turn top/bottom surfaces to internal
+    if (this->_region->config.top_solid_layers == 0) {
+        for (Surfaces::iterator surface = this->fill_surfaces.surfaces.begin(); surface != this->fill_surfaces.surfaces.end(); ++surface) {
+            if (surface->surface_type == stTop)
+                surface->surface_type = stInternal;
+        }
+    }
+    if (this->_region->config.bottom_solid_layers == 0) {
+        for (Surfaces::iterator surface = this->fill_surfaces.surfaces.begin(); surface != this->fill_surfaces.surfaces.end(); ++surface) {
+            if (surface->surface_type == stBottom || surface->surface_type == stBottomBridge)
+                surface->surface_type = stInternal;
+        }
+    }
+        
+    // turn too small internal regions into solid regions according to the user setting
+    if (this->_region->config.fill_density.value > 0) {
+        // scaling an area requires two calls!
+        double min_area = scale_(scale_(this->_region->config.solid_infill_below_area.value));
+        for (Surfaces::iterator surface = this->fill_surfaces.surfaces.begin(); surface != this->fill_surfaces.surfaces.end(); ++surface) {
+            if (surface->surface_type == stInternal && surface->area() <= min_area)
+                surface->surface_type = stInternalSolid;
+        }
+    }
+}
+
 #ifdef SLIC3RXS
 REGISTER_CLASS(LayerRegion, "Layer::Region");
 #endif
diff --git a/xs/xsp/Layer.xsp b/xs/xsp/Layer.xsp
index a48f8d156..611e2cae9 100644
--- a/xs/xsp/Layer.xsp
+++ b/xs/xsp/Layer.xsp
@@ -29,6 +29,7 @@
     Clone<Flow> flow(FlowRole role, bool bridge = false, double width = -1)
         %code%{ RETVAL = THIS->flow(role, bridge, width); %};
     void merge_slices();
+    void prepare_fill_surfaces();
 };
 
 %name{Slic3r::Layer} class Layer {