diff --git a/tests/system-test/2-query/diff.py b/tests/system-test/2-query/diff.py
index d48a01db6a..126b4e5d63 100644
--- a/tests/system-test/2-query/diff.py
+++ b/tests/system-test/2-query/diff.py
@@ -52,6 +52,95 @@ class TDTestCase:
         tdSql.checkData(0, 0, None)
         tdSql.checkData(1, 0, None)
 
+        # handle null values
+        tdSql.execute(
+            f"create table {dbname}.ntb_null(ts timestamp,c1 int,c2 double,c3 float,c4 bool)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, 1,    1.0,  NULL, NULL)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, NULL, 2.0,  2.0,  NULL)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, 2,    NULL, NULL, false)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, NULL, 1.0,  1.0,  NULL)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, NULL, 3.0,  NULL, true)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, 3,    NULL, 3.0,  NULL)")
+        tdSql.execute(f"insert into {dbname}.ntb_null values(now, 1,    NULL, NULL, true)")
+
+        tdSql.query(f"select diff(c1) from {dbname}.ntb_null")
+        tdSql.checkRows(6)
+        tdSql.checkData(0, 0, None)
+        tdSql.checkData(1, 0, 1)
+        tdSql.checkData(2, 0, None)
+        tdSql.checkData(3, 0, None)
+        tdSql.checkData(4, 0, 1)
+        tdSql.checkData(5, 0, -2)
+
+        tdSql.query(f"select diff(c2) from {dbname}.ntb_null")
+        tdSql.checkRows(6)
+        tdSql.checkData(0, 0, 1)
+        tdSql.checkData(1, 0, None)
+        tdSql.checkData(2, 0, -1)
+        tdSql.checkData(3, 0, 2)
+        tdSql.checkData(4, 0, None)
+        tdSql.checkData(5, 0, None)
+
+        tdSql.query(f"select diff(c3) from {dbname}.ntb_null")
+        tdSql.checkRows(6)
+        tdSql.checkData(0, 0, None)
+        tdSql.checkData(1, 0, None)
+        tdSql.checkData(2, 0, -1)
+        tdSql.checkData(3, 0, None)
+        tdSql.checkData(4, 0, 2)
+        tdSql.checkData(5, 0, None)
+
+        tdSql.query(f"select diff(c4) from {dbname}.ntb_null")
+        tdSql.checkRows(6)
+        tdSql.checkData(0, 0, None)
+        tdSql.checkData(1, 0, None)
+        tdSql.checkData(2, 0, None)
+        tdSql.checkData(3, 0, 1)
+        tdSql.checkData(4, 0, None)
+        tdSql.checkData(5, 0, 0)
+
+        tdSql.query(f"select diff(c1),diff(c2),diff(c3),diff(c4) from {dbname}.ntb_null")
+        tdSql.checkRows(6)
+        tdSql.checkData(0, 0, None)
+        tdSql.checkData(1, 0, 1)
+        tdSql.checkData(2, 0, None)
+        tdSql.checkData(3, 0, None)
+        tdSql.checkData(4, 0, 1)
+        tdSql.checkData(5, 0, -2)
+        tdSql.checkData(0, 1, 1)
+        tdSql.checkData(1, 1, None)
+        tdSql.checkData(2, 1, -1)
+        tdSql.checkData(3, 1, 2)
+        tdSql.checkData(4, 1, None)
+        tdSql.checkData(5, 1, None)
+        tdSql.checkData(0, 2, None)
+        tdSql.checkData(1, 2, None)
+        tdSql.checkData(2, 2, -1)
+        tdSql.checkData(3, 2, None)
+        tdSql.checkData(4, 2, 2)
+        tdSql.checkData(5, 2, None)
+        tdSql.checkData(0, 3, None)
+        tdSql.checkData(1, 3, None)
+        tdSql.checkData(2, 3, None)
+        tdSql.checkData(3, 3, 1)
+        tdSql.checkData(4, 3, None)
+        tdSql.checkData(5, 3, 0)
+
+        tdSql.query(f"select diff(c1),diff(c2),diff(c3),diff(c4) from {dbname}.ntb_null where c1 is not null")
+        tdSql.checkRows(3)
+        tdSql.checkData(0, 0, 1)
+        tdSql.checkData(1, 0, 1)
+        tdSql.checkData(2, 0, -2)
+        tdSql.checkData(0, 1, None)
+        tdSql.checkData(1, 1, None)
+        tdSql.checkData(2, 1, None)
+        tdSql.checkData(0, 2, None)
+        tdSql.checkData(1, 2, None)
+        tdSql.checkData(2, 2, None)
+        tdSql.checkData(0, 3, None)
+        tdSql.checkData(1, 3, None)
+        tdSql.checkData(2, 3, 1)
+
         tdSql.execute(f'''create table {dbname}.stb(ts timestamp, col1 tinyint, col2 smallint, col3 int, col4 bigint, col5 float, col6 double,
                     col7 bool, col8 binary(20), col9 nchar(20), col11 tinyint unsigned, col12 smallint unsigned, col13 int unsigned, col14 bigint unsigned) tags(loc nchar(20))''')
         tdSql.execute(f"create table {dbname}.stb_1 using {dbname}.stb tags('beijing')")