diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index cdf26c9e0..c381ce95c 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -625,11 +625,14 @@ EOF
 
 sub make_skirt {
     my $self = shift;
+    
+    # since this method must be idempotent, we clear skirt paths *before*
+    # checking whether we need to generate them
+    $self->skirt->clear;
+    
     return unless $self->config->skirts > 0
         || ($self->config->ooze_prevention && @{$self->extruders} > 1);
     
-    $self->skirt->clear;  # method must be idempotent
-    
     # First off we need to decide how tall the skirt must be.
     # The skirt_height option from config is expressed in layers, but our
     # object might have different layer heights, so we need to find the print_z
@@ -737,9 +740,12 @@ sub make_skirt {
 
 sub make_brim {
     my $self = shift;
-    return unless $self->config->brim_width > 0;
     
-    $self->brim->clear;  # method must be idempotent
+    # since this method must be idempotent, we clear brim paths *before*
+    # checking whether we need to generate them
+    $self->brim->clear;
+    
+    return unless $self->config->brim_width > 0;
     
     # brim is only printed on first layer and uses support material extruder
     my $first_layer_height = $self->objects->[0]->config->get_abs_value('first_layer_height');
diff --git a/lib/Slic3r/Print/Object.pm b/lib/Slic3r/Print/Object.pm
index a43123a88..61b3da837 100644
--- a/lib/Slic3r/Print/Object.pm
+++ b/lib/Slic3r/Print/Object.pm
@@ -965,6 +965,9 @@ sub combine_infill {
 
 sub generate_support_material {
     my $self = shift;
+    
+    # TODO: make this method idempotent by removing all support layers
+    # before checking whether we need to generate support or not
     return unless ($self->config->support_material || $self->config->raft_layers > 0)
         && scalar(@{$self->layers}) >= 2;