diff --git a/pyext/ctools/__init__.py.in b/pyext/ctools/__init__.py.in
index 6973fa3..e6c4661 100755
--- a/pyext/ctools/__init__.py.in
+++ b/pyext/ctools/__init__.py.in
@@ -1,7 +1,7 @@
 # ==========================================================================
 # ctools Python module
 #
-# Copyright (C) 2015-2016 Juergen Knoedlseder
+# Copyright (C) 2015-2021 Juergen Knoedlseder
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -26,14 +26,15 @@ from @PYTHON_RELATIVE_IMPORT@tools import *
 # Remove swig register stuff
 bad_entries = [entry for entry in list(locals())
                if entry.endswith('_swigregister')]
-for entry in bad_entries:
-    del locals()[entry]
+if len(bad_entries) > 0:
+    for entry in bad_entries:
+        del locals()[entry]
+    del entry
 
 # Clean-up
 del tools
 del gammalib
 del bad_entries
-del entry
 
 # Add version
 __version__ = '@PACKAGE_VERSION@'