diff --git a/cura/LayerPolygon.py b/cura/LayerPolygon.py
index e31e85b485..07f6660388 100644
--- a/cura/LayerPolygon.py
+++ b/cura/LayerPolygon.py
@@ -42,7 +42,7 @@ class LayerPolygon:
 
         self._extruder = extruder
         self._types = line_types
-        unknown_types = numpy.where(self._types >= self.__number_of_types)
+        unknown_types = numpy.where(self._types >= self.__number_of_types, self._types)
         if unknown_types:
             # Got faulty line data from the engine.
             for idx in unknown_types: