diff --git a/lib/Slic3r/Layer/Region.pm b/lib/Slic3r/Layer/Region.pm
index f4c425a19..798fe363a 100644
--- a/lib/Slic3r/Layer/Region.pm
+++ b/lib/Slic3r/Layer/Region.pm
@@ -99,6 +99,7 @@ sub make_perimeters {
                         my $diff = diff_ex(
                             \@last,
                             offset(\@offsets, +0.5*$pwidth),
+                            1,  # medial axis requires non-overlapping geometry
                         );
                         push @thin_walls, @$diff;
                     }
@@ -222,9 +223,6 @@ sub make_perimeters {
     $self->perimeters->append(@loops);
     
     # process thin walls by collapsing slices to single passes
-    my $min_thin_wall_width = $pwidth/3;
-    my $min_thin_wall_length = 2*$pwidth;
-    #@thin_walls = @{offset2_ex([ map @$_, @thin_walls ], -0.5*$min_thin_wall_width, +0.5*$min_thin_wall_width)};
     if (@thin_walls) {
         my @p = map @{$_->medial_axis($pspacing)}, @thin_walls;
         
@@ -240,6 +238,7 @@ sub make_perimeters {
         }
         
         my @paths = ();
+        my $min_thin_wall_length = 2*$pwidth;
         for my $p (@p) {
             next if $p->length < $min_thin_wall_length;
             my %params = (
diff --git a/xs/src/Geometry.cpp b/xs/src/Geometry.cpp
index a4ff2f24d..c324a162c 100644
--- a/xs/src/Geometry.cpp
+++ b/xs/src/Geometry.cpp
@@ -237,7 +237,7 @@ MedialAxis::is_valid_edge(const VD::edge_type& edge) const
     // if we only process segments representing closed loops, none if the
     // infinite edges (if any) would be part of our MAT anyway
     if (edge.is_secondary() || edge.is_infinite()) return false;
-        
+    
     /* If the cells sharing this edge have a common vertex, we're not interested
        in this edge. Why? Because it means that the edge lies on the bisector of
        two contiguous input lines and it was included in the Voronoi graph because