diff --git a/invesalius/control.py b/invesalius/control.py
index 025c5a9..5a42e69 100644
--- a/invesalius/control.py
+++ b/invesalius/control.py
@@ -965,7 +965,7 @@ class Controller():
                 re_dialog = dialog.ResizeImageDialog()
                 re_dialog.SetValue(int(resolution_percentage*100))
                 re_dialog_value = re_dialog.ShowModal()
-                re_dialog.Close() 
+                re_dialog.Close()
 
                 if re_dialog_value == wx.ID_OK:
                     percentage = re_dialog.GetValue()
@@ -1143,7 +1143,7 @@ class Controller():
     def show_mask_preview(self, index, flag=True):
         proj = prj.Project()
         mask = proj.mask_dict[index]
-        slc = self.Slice.do_threshold_to_all_slices(mask)
+        self.Slice.do_threshold_to_all_slices(mask)
         mask.create_3d_preview()
         Publisher.sendMessage("Load mask preview", mask_3d_actor=mask.volume._actor, flag=flag)
         Publisher.sendMessage("Reload actual slice")
diff --git a/invesalius/data/slice_.py b/invesalius/data/slice_.py
index e5a0ba1..84aff4e 100644
--- a/invesalius/data/slice_.py
+++ b/invesalius/data/slice_.py
@@ -1185,6 +1185,7 @@ class Slice(metaclass=utils.Singleton):
         future_mask = proj.GetMask(index)
         future_mask.is_shown = True
         self.current_mask = future_mask
+        self.current_mask.on_show()
 
         colour = future_mask.colour
         self.SetMaskColour(index, colour, update=False)
--
libgit2 0.21.2