diff --git a/cura/CuraApplication.py b/cura/CuraApplication.py
index 7645e88b7e..4285f9ac1d 100755
--- a/cura/CuraApplication.py
+++ b/cura/CuraApplication.py
@@ -43,7 +43,7 @@ from UM.Scene.Selection import Selection
 from UM.Scene.ToolHandle import ToolHandle
 from UM.Settings.ContainerRegistry import ContainerRegistry
 from UM.Settings.InstanceContainer import InstanceContainer
-from UM.Settings.SettingDefinition import SettingDefinition, DefinitionPropertyType
+from UM.Settings.SettingDefinition import SettingDefinition, DefinitionPropertyType, toIntConversion
 from UM.Settings.SettingFunction import SettingFunction
 from UM.Settings.Validator import Validator
 from UM.View.SelectionPass import SelectionPass  # For typing.
@@ -382,11 +382,12 @@ class CuraApplication(QtApplication):
         SettingDefinition.addSupportedProperty("resolve", DefinitionPropertyType.Function, default=None,
                                                depends_on="value")
 
-        SettingDefinition.addSettingType("extruder", None, str, Validator)
-        SettingDefinition.addSettingType("optional_extruder", None, str, None)
+        SettingDefinition.addSettingType("extruder", None, toIntConversion, Validator)
+        SettingDefinition.addSettingType("optional_extruder", None, toIntConversion, None)
         SettingDefinition.addSettingType("[int]", None, str, None)
 
 
+
     def _initializeSettingFunctions(self):
         """Adds custom property types, settings types, and extra operators (functions).