diff -r f13799fbcfea -r fcbd6b251d81 cubicweb/server/session.py
--- a/cubicweb/server/session.py	Mon Jan 23 15:35:19 2017 +0100
+++ b/cubicweb/server/session.py	Fri Jan 27 16:26:09 2017 +0100
@@ -43,6 +43,8 @@
 
 NO_UNDO_TYPES = schema.SCHEMA_TYPES.copy()
 NO_UNDO_TYPES.add('CWCache')
+NO_UNDO_TYPES.add('CWSession')
+NO_UNDO_TYPES.add('CWDataImport')
 # is / is_instance_of are usually added by sql hooks except when using
 # dataimport.NoHookRQLObjectStore, and we don't want to record them
 # anyway in the later case