diff -r 21fae1546ac4 -r 94dc8ccd320b server/test/unittest_rql2sql.py
--- a/server/test/unittest_rql2sql.py	Tue May 19 11:18:05 2009 +0200
+++ b/server/test/unittest_rql2sql.py	Tue May 19 13:08:51 2009 +0200
@@ -1,3 +1,4 @@
+
 """unit tests for module cubicweb.server.sources.rql2sql"""
 
 import sys
@@ -1211,6 +1212,14 @@
 WHERE rel_in_group0.eid_from=T00.x AND rel_in_group0.eid_to=G.cw_eid''',
                     varmap={'X': 'T00.x', 'X.login': 'T00.l'})
 
+    def test_is_null_transform(self):
+        union = self._prepare('Any X WHERE X login %(login)s')
+        r, args = self.o.generate(union, {'login': None})
+        self.assertLinesEquals((r % args).strip(),
+                               '''SELECT X.cw_eid
+FROM cw_CWUser AS X
+WHERE X.cw_login IS NULL''')
+
     def test_parser_parse(self):
         for t in self._parse(PARSER):
             yield t