diff --git a/source/libs/function/src/builtins.c b/source/libs/function/src/builtins.c
index 51d51db6e8..be94352f29 100644
--- a/source/libs/function/src/builtins.c
+++ b/source/libs/function/src/builtins.c
@@ -2925,7 +2925,7 @@ const SBuiltinFuncDefinition funcMgtBuiltins[] = {
   {
     .name = "unique",
     .type = FUNCTION_TYPE_UNIQUE,
-    .classification = FUNC_MGT_SELECT_FUNC | FUNC_MGT_INDEFINITE_ROWS_FUNC | FUNC_MGT_FORBID_STREAM_FUNC,
+    .classification = FUNC_MGT_SELECT_FUNC | FUNC_MGT_INDEFINITE_ROWS_FUNC | FUNC_MGT_FORBID_STREAM_FUNC | FUNC_MGT_IMPLICIT_TS_FUNC,
     .translateFunc = translateUnique,
     .getEnvFunc   = getUniqueFuncEnv,
     .initFunc     = uniqueFunctionSetup,
diff --git a/tests/system-test/2-query/unique.py b/tests/system-test/2-query/unique.py
index a3238ce8d1..b3053817d3 100644
--- a/tests/system-test/2-query/unique.py
+++ b/tests/system-test/2-query/unique.py
@@ -438,13 +438,13 @@ class TDTestCase:
         tdSql.checkData(0,0,4)
         tdSql.checkData(1,0,1)
 
-        tdSql.query(f"select  unique(c1) v from (select c1 from  {dbname}.ct1 partition by c2)")
+        tdSql.query(f"select  unique(c1) v from (select _rowts, c1 from  {dbname}.ct1 partition by c2)")
         tdSql.checkRows(10)
 
-        tdSql.query(f"select  unique(c1) v from (select c1 from  {dbname}.ct1 order by c2)")
+        tdSql.query(f"select  unique(c1) v from (select _rowts, c1 from  {dbname}.ct1 order by c2)")
         tdSql.checkRows(10)
 
-        tdSql.query(f"select  unique(c1) v from (select c1 from  {dbname}.ct1 union all select c1 from {dbname}.ct1)")
+        tdSql.query(f"select  unique(c1) v from (select _rowts, c1 from  {dbname}.ct1 union all select _rowts, c1 from {dbname}.ct1)")
         tdSql.checkRows(10)
 
         # TD-19911