diff --git a/invesalius/data/mask.py b/invesalius/data/mask.py
index 9988aa6..2212396 100644
--- a/invesalius/data/mask.py
+++ b/invesalius/data/mask.py
@@ -291,3 +291,4 @@ class Mask():
     def __del__(self):
         if self.is_shown:
             self.history._config_undo_redo(False)
+        os.remove(self.temp_file)
diff --git a/invesalius/data/slice_.py b/invesalius/data/slice_.py
index 8c8d812..805259d 100644
--- a/invesalius/data/slice_.py
+++ b/invesalius/data/slice_.py
@@ -243,6 +243,9 @@ class Slice(object):
 
     def CloseProject(self):
         self.imagedata = None
+        f = self._matrix.filename
+        self._matrix  = None
+        os.remove(f)
         self.current_mask = None
 
         self.values = None
--
libgit2 0.21.2