diff --git a/tests/system-test/2-query/concat.py b/tests/system-test/2-query/concat.py
index 326f6940f6..b43d4fafa8 100644
--- a/tests/system-test/2-query/concat.py
+++ b/tests/system-test/2-query/concat.py
@@ -144,6 +144,9 @@ class TDTestCase:
             f"{dbname}.ct2",
             f"{dbname}.ct4",
         ]
+        tdSql.query("select concat(null,null)")  # TD-31571
+        tdSql.checkRows(1)
+        tdSql.checkData(0, 0, None)
         for tb in tbname:
             for i in range(2,8):
                 self.__concat_check(tb,i)
diff --git a/tests/system-test/2-query/concat_ws.py b/tests/system-test/2-query/concat_ws.py
index 26731715c1..338166c61e 100644
--- a/tests/system-test/2-query/concat_ws.py
+++ b/tests/system-test/2-query/concat_ws.py
@@ -156,7 +156,9 @@ class TDTestCase:
             f"{dbname}.ct2",
             f"{dbname}.ct4",
         ]
-
+        tdSql.query("select concat_ws(null,null,null);")  # TD-31572
+        tdSql.checkRows(1)
+        tdSql.checkData(0, 0, None)
         for tb in tbname:
             for errsql in self.__concat_ws_err_check(tb):
                 tdSql.error(sql=errsql)