diff --git a/pyext/ctools/__init__.py b/pyext/ctools/__init__.py
index 1f98b39..1d6af6e 100644
--- a/pyext/ctools/__init__.py
+++ b/pyext/ctools/__init__.py
@@ -1,3 +1,9 @@
 from .ctools import *
 import obsutils
 
+bad_entries = [entry for entry in list(locals())
+               if entry.endswith('_swigregister')]
+for entry in bad_entries:
+    del locals()[entry]
+del gammalib
+del ctools