diff --git a/cura/PrintInformation.py b/cura/PrintInformation.py
index cfd1e3fd3b..7b4b43eb14 100644
--- a/cura/PrintInformation.py
+++ b/cura/PrintInformation.py
@@ -110,7 +110,6 @@ class PrintInformation(QObject):
 
         self._print_time_message_values = {}
 
-
     def _initPrintTimeMessageValues(self, build_plate_number):
         # Full fill message values using keys from _print_time_message_translations
         self._print_time_message_values[build_plate_number] = {}
diff --git a/plugins/CuraEngineBackend/CuraEngineBackend.py b/plugins/CuraEngineBackend/CuraEngineBackend.py
index 95712b291a..1c275d6d5b 100755
--- a/plugins/CuraEngineBackend/CuraEngineBackend.py
+++ b/plugins/CuraEngineBackend/CuraEngineBackend.py
@@ -540,6 +540,8 @@ class CuraEngineBackend(QObject, Backend):
     #
     #   \param message The protobuf message containing sliced layer data.
     def _onOptimizedLayerMessage(self, message):
+        if self._start_slice_job_build_plate not in self._stored_optimized_layer_data:
+            self._stored_optimized_layer_data[self._start_slice_job_build_plate] = []
         self._stored_optimized_layer_data[self._start_slice_job_build_plate].append(message)
 
     ##  Called when a progress message is received from the engine.