diff --git a/pkg/session/session.go b/pkg/session/session.go
index f8cefa8866273..d3de4ad6a1588 100644
--- a/pkg/session/session.go
+++ b/pkg/session/session.go
@@ -1186,10 +1186,6 @@ func createSessionFunc(store kv.Storage) pools.Factory {
 		if err != nil {
 			return nil, errors.Trace(err)
 		}
-		err = se.sessionVars.SetSystemVar(variable.TiDBEnableWindowFunction, variable.BoolToOnOff(variable.DefEnableWindowFunction))
-		if err != nil {
-			return nil, errors.Trace(err)
-		}
 		err = se.sessionVars.SetSystemVar(variable.TiDBConstraintCheckInPlacePessimistic, variable.On)
 		if err != nil {
 			return nil, errors.Trace(err)
diff --git a/pkg/sessionctx/variable/session.go b/pkg/sessionctx/variable/session.go
index a3d0b7f8dd556..7c66d9797f3ef 100644
--- a/pkg/sessionctx/variable/session.go
+++ b/pkg/sessionctx/variable/session.go
@@ -2213,6 +2213,7 @@ func NewSessionVars(hctx HookContext) *SessionVars {
 		DefaultCollationForUTF8MB4:    mysql.DefaultCollationName,
 		GroupConcatMaxLen:             DefGroupConcatMaxLen,
 		EnableRedactLog:               DefTiDBRedactLog,
+		EnableWindowFunction:          DefEnableWindowFunction,
 	}
 	vars.status.Store(uint32(mysql.ServerStatusAutocommit))
 	vars.StmtCtx.ResourceGroupName = resourcegroup.DefaultResourceGroupName
diff --git a/pkg/sessionctx/variable/sysvar_test.go b/pkg/sessionctx/variable/sysvar_test.go
index be32ef1d2933e..b2739f8d9d92a 100644
--- a/pkg/sessionctx/variable/sysvar_test.go
+++ b/pkg/sessionctx/variable/sysvar_test.go
@@ -1742,6 +1742,17 @@ func TestTiDBSchemaCacheSize(t *testing.T) {
 	require.Error(t, err)
 }
 
+func TestEnableWindowFunction(t *testing.T) {
+	vars := NewSessionVars(nil)
+	require.Equal(t, vars.EnableWindowFunction, DefEnableWindowFunction)
+	require.NoError(t, vars.SetSystemVar(TiDBEnableWindowFunction, "on"))
+	require.Equal(t, vars.EnableWindowFunction, true)
+	require.NoError(t, vars.SetSystemVar(TiDBEnableWindowFunction, "0"))
+	require.Equal(t, vars.EnableWindowFunction, false)
+	require.NoError(t, vars.SetSystemVar(TiDBEnableWindowFunction, "1"))
+	require.Equal(t, vars.EnableWindowFunction, true)
+}
+
 func TestTiDBAutoAnalyzeConcurrencyValidation(t *testing.T) {
 	vars := NewSessionVars(nil)