diff --git a/pkg/session/session.go b/pkg/session/session.go
index 797c0caebfe02..f18ce5ccfe574 100644
--- a/pkg/session/session.go
+++ b/pkg/session/session.go
@@ -1317,10 +1317,6 @@ 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 2435ab8e7af8f..e7bc825cb36f3 100644
--- a/pkg/sessionctx/variable/session.go
+++ b/pkg/sessionctx/variable/session.go
@@ -2022,6 +2022,7 @@ func NewSessionVars(hctx HookContext) *SessionVars {
 		TiFlashComputeDispatchPolicy:  tiflashcompute.DispatchPolicyConsistentHash,
 		ResourceGroupName:             resourcegroup.DefaultResourceGroupName,
 		DefaultCollationForUTF8MB4:    mysql.DefaultCollationName,
+		EnableWindowFunction:          DefEnableWindowFunction,
 	}
 	vars.KVVars = tikvstore.NewVariables(&vars.Killed)
 	vars.StmtCtx.ResourceGroupName = resourcegroup.DefaultResourceGroupName
diff --git a/pkg/sessionctx/variable/sysvar_test.go b/pkg/sessionctx/variable/sysvar_test.go
index baaf037dad7f5..8b00eacb89fde 100644
--- a/pkg/sessionctx/variable/sysvar_test.go
+++ b/pkg/sessionctx/variable/sysvar_test.go
@@ -1437,3 +1437,14 @@ func TestSetTiDBCloudStorageURI(t *testing.T) {
 	require.Len(t, val, 0)
 	cancel()
 }
+
+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)
+}