diff --git a/lib/Slic3r/GUI/Plater.pm b/lib/Slic3r/GUI/Plater.pm
index d7bb3195df..30745ab806 100644
--- a/lib/Slic3r/GUI/Plater.pm
+++ b/lib/Slic3r/GUI/Plater.pm
@@ -840,6 +840,7 @@ sub set_number_of_copies {
     
     # prompt user
     my $copies = Wx::GetNumberFromUser("", "Enter the number of copies of the selected object:", "Copies", $model_object->instances_count, 0, 1000, $self);
+    return if $copies == -1;
     my $diff = $copies - $model_object->instances_count;
     if ($diff == 0) {
         # no variation