diff --git a/plugins/PerObjectSettingsTool/PerObjectSettingVisibilityHandler.py b/plugins/PerObjectSettingsTool/PerObjectSettingVisibilityHandler.py
index ea64ddbb35..78da0512f7 100644
--- a/plugins/PerObjectSettingsTool/PerObjectSettingVisibilityHandler.py
+++ b/plugins/PerObjectSettingsTool/PerObjectSettingVisibilityHandler.py
@@ -71,7 +71,7 @@ class PerObjectSettingVisibilityHandler(UM.Settings.Models.SettingVisibilityHand
 
         # Add all instances that are not added, but are in visibility list
         for item in visible:
-            if settings.getInstance(item) is not None:  # Setting was not added already.
+            if settings.getInstance(item) is None:  # Setting was not added already.
                 definition = self._stack.getSettingDefinition(item)
                 if definition:
                     new_instance = SettingInstance(definition, settings)
diff --git a/plugins/PerObjectSettingsTool/PerObjectSettingsTool.py b/plugins/PerObjectSettingsTool/PerObjectSettingsTool.py
index 09ace28d37..84ed312295 100644
--- a/plugins/PerObjectSettingsTool/PerObjectSettingsTool.py
+++ b/plugins/PerObjectSettingsTool/PerObjectSettingsTool.py
@@ -97,7 +97,7 @@ class PerObjectSettingsTool(Tool):
 
         for property_key in ["top_bottom_thickness", "wall_thickness"]:
             if mesh_type == "infill_mesh":
-                if not settings.getInstance(property_key):
+                if settings.getInstance(property_key) is None:
                     definition = stack.getSettingDefinition(property_key)
                     new_instance = SettingInstance(definition, settings)
                     new_instance.setProperty("value", 0)