diff --git a/tests/system-test/2-query/join.py b/tests/system-test/2-query/join.py
index 57e433804d731cd06d9d57182c791f13af9f2f0e..61c0ecbf2c3e4d092cafc376a7788e07f336d44b 100644
--- a/tests/system-test/2-query/join.py
+++ b/tests/system-test/2-query/join.py
@@ -102,7 +102,7 @@ class TDTestCase:
                 if len(tblist) == 2:
                     if "ct1" in tblist or "t1" in tblist:
                         self.__join_current(sql, checkrows)
-                    elif where_condition:
+                    elif where_condition or "null" in groups:
                         self.__join_current(sql, checkrows + 2 )
                     else:
                         self.__join_current(sql, checkrows + 5 )