diff --git a/executor/aggregate_test.go b/executor/aggregate_test.go
index 81848934ea075..3e84256d79138 100644
--- a/executor/aggregate_test.go
+++ b/executor/aggregate_test.go
@@ -1374,6 +1374,26 @@ func (s *testSuiteAgg) TestIssue20658(c *C) {
 	}
 }
 
+func (s *testSuiteAgg) TestAvgDecimal(c *C) {
+	tk := testkit.NewTestKitWithInit(c, s.store)
+	tk.MustExec("use test;")
+	tk.MustExec("drop table if exists td;")
+	tk.MustExec("create table td (col_bigint bigint(20), col_smallint smallint(6));")
+	tk.MustExec("insert into td values (null, 22876);")
+	tk.MustExec("insert into td values (9220557287087669248, 32767);")
+	tk.MustExec("insert into td values (28030, 32767);")
+	tk.MustExec("insert into td values (-3309864251140603904,32767);")
+	tk.MustExec("insert into td values (4,0);")
+	tk.MustExec("insert into td values (null,0);")
+	tk.MustExec("insert into td values (4,-23828);")
+	tk.MustExec("insert into td values (54720,32767);")
+	tk.MustExec("insert into td values (0,29815);")
+	tk.MustExec("insert into td values (10017,-32661);")
+	tk.MustQuery(" SELECT AVG( col_bigint / col_smallint) AS field1 FROM td;").Sort().Check(testkit.Rows("25769363061037.62077260"))
+	tk.MustQuery(" SELECT AVG(col_bigint) OVER (PARTITION BY col_smallint) as field2 FROM td where col_smallint = -23828;").Sort().Check(testkit.Rows("4.0000"))
+	tk.MustExec("drop table td;")
+}
+
 func (s *testSerialSuite) TestRandomPanicAggConsume(c *C) {
 	tk := testkit.NewTestKitWithInit(c, s.store)
 	tk.MustExec("set @@tidb_max_chunk_size=32")
diff --git a/executor/builder.go b/executor/builder.go
index ac491fa44e080..85eb1e63ce26f 100644
--- a/executor/builder.go
+++ b/executor/builder.go
@@ -3911,7 +3911,7 @@ func (b *executorBuilder) buildWindow(v *plannercore.PhysicalWindow) Executor {
 	partialResults := make([]aggfuncs.PartialResult, 0, len(v.WindowFuncDescs))
 	resultColIdx := v.Schema().Len() - len(v.WindowFuncDescs)
 	for _, desc := range v.WindowFuncDescs {
-		aggDesc, err := aggregation.NewAggFuncDesc(b.ctx, desc.Name, desc.Args, false)
+		aggDesc, err := aggregation.NewAggFuncDescForWindowFunc(b.ctx, desc, false)
 		if err != nil {
 			b.err = err
 			return nil
diff --git a/executor/tiflash_test.go b/executor/tiflash_test.go
index a61c735a5f534..1e618181d40ba 100644
--- a/executor/tiflash_test.go
+++ b/executor/tiflash_test.go
@@ -690,6 +690,34 @@ func (s *tiflashTestSuite) TestMppUnionAll(c *C) {
 
 }
 
+func (s *tiflashTestSuite) TestAvgOverflow(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+
+	// avg decimal
+	tk.MustExec("drop table if exists td;")
+	tk.MustExec("create table td (col_bigint bigint(20), col_smallint smallint(6));")
+	tk.MustExec("alter table td set tiflash replica 1")
+	tb := testGetTableByName(c, tk.Se, "test", "td")
+	err := domain.GetDomain(tk.Se).DDL().UpdateTableReplicaInfo(tk.Se, tb.Meta().ID, true)
+	c.Assert(err, IsNil)
+	tk.MustExec("insert into td values (null, 22876);")
+	tk.MustExec("insert into td values (9220557287087669248, 32767);")
+	tk.MustExec("insert into td values (28030, 32767);")
+	tk.MustExec("insert into td values (-3309864251140603904,32767);")
+	tk.MustExec("insert into td values (4,0);")
+	tk.MustExec("insert into td values (null,0);")
+	tk.MustExec("insert into td values (4,-23828);")
+	tk.MustExec("insert into td values (54720,32767);")
+	tk.MustExec("insert into td values (0,29815);")
+	tk.MustExec("insert into td values (10017,-32661);")
+	tk.MustExec("set @@session.tidb_isolation_read_engines=\"tiflash\"")
+	tk.MustExec("set @@session.tidb_enforce_mpp=ON")
+	tk.MustQuery(" SELECT AVG( col_bigint / col_smallint) AS field1 FROM td;").Sort().Check(testkit.Rows("25769363061037.62077260"))
+	tk.MustQuery(" SELECT AVG(col_bigint) OVER (PARTITION BY col_smallint) as field2 FROM td where col_smallint = -23828;").Sort().Check(testkit.Rows("4.0000"))
+	tk.MustExec("drop table if exists td;")
+}
+
 func (s *tiflashTestSuite) TestUnionWithEmptyDualTable(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")
diff --git a/expression/aggregation/descriptor.go b/expression/aggregation/descriptor.go
index 4415b0688ce09..ba2c24a98a67f 100644
--- a/expression/aggregation/descriptor.go
+++ b/expression/aggregation/descriptor.go
@@ -41,6 +41,7 @@ type AggFuncDesc struct {
 }
 
 // NewAggFuncDesc creates an aggregation function signature descriptor.
+// this func cannot be called twice as the TypeInfer has changed the type of args in the first time.
 func NewAggFuncDesc(ctx sessionctx.Context, name string, args []expression.Expression, hasDistinct bool) (*AggFuncDesc, error) {
 	b, err := newBaseFuncDesc(ctx, name, args)
 	if err != nil {
@@ -49,6 +50,14 @@ func NewAggFuncDesc(ctx sessionctx.Context, name string, args []expression.Expre
 	return &AggFuncDesc{baseFuncDesc: b, HasDistinct: hasDistinct}, nil
 }
 
+// NewAggFuncDescForWindowFunc creates an aggregation function from window functions, where baseFuncDesc may be ready.
+func NewAggFuncDescForWindowFunc(ctx sessionctx.Context, Desc *WindowFuncDesc, hasDistinct bool) (*AggFuncDesc, error) {
+	if Desc.RetTp == nil { // safety check
+		return NewAggFuncDesc(ctx, Desc.Name, Desc.Args, hasDistinct)
+	}
+	return &AggFuncDesc{baseFuncDesc: baseFuncDesc{Desc.Name, Desc.Args, Desc.RetTp}, HasDistinct: hasDistinct}, nil
+}
+
 // String implements the fmt.Stringer interface.
 func (a *AggFuncDesc) String() string {
 	buffer := bytes.NewBufferString(a.Name)