diff --git a/lib/Slic3r/GUI/Plater.pm b/lib/Slic3r/GUI/Plater.pm
index b93e49038..5fb3b29f4 100644
--- a/lib/Slic3r/GUI/Plater.pm
+++ b/lib/Slic3r/GUI/Plater.pm
@@ -656,7 +656,7 @@ sub load_presets {
             }
             
             my $selected = shift @sel;
-            if ($selected <= $#presets) {
+            if (defined $selected && $selected <= $#presets) {
                 # call SetSelection() only after SetString() otherwise the new string
                 # won't be picked up as the visible string
                 $choice->SetSelection($selected);
diff --git a/lib/Slic3r/GUI/Preset.pm b/lib/Slic3r/GUI/Preset.pm
index 35208f585..d855c3c60 100644
--- a/lib/Slic3r/GUI/Preset.pm
+++ b/lib/Slic3r/GUI/Preset.pm
@@ -33,7 +33,7 @@ sub config {
                 for grep $external_config->has($_), @$keys;
             
             # For extra_keys we don't populate defaults.
-            if ($extra_keys) {
+            if ($extra_keys && !$self->external) {
                 $config->set($_, $external_config->get($_))
                     for grep $external_config->has($_), @$extra_keys;
             }