diff --git a/sessionctx/variable/session.go b/sessionctx/variable/session.go
index 8cfe1854edef7..c0318adf56a13 100644
--- a/sessionctx/variable/session.go
+++ b/sessionctx/variable/session.go
@@ -1727,6 +1727,7 @@ func NewSessionVars(hctx HookContext) *SessionVars {
 		EnableReuseCheck:              DefTiDBEnableReusechunk,
 		preUseChunkAlloc:              DefTiDBUseAlloc,
 		ChunkPool:                     ReuseChunkPool{Alloc: nil},
+		EnableWindowFunction:          DefEnableWindowFunction,
 	}
 	vars.KVVars = tikvstore.NewVariables(&vars.Killed)
 	vars.Concurrency = Concurrency{
diff --git a/sessionctx/variable/sysvar_test.go b/sessionctx/variable/sysvar_test.go
index f6da8c87495c7..6f3af221dbdc7 100644
--- a/sessionctx/variable/sysvar_test.go
+++ b/sessionctx/variable/sysvar_test.go
@@ -1092,3 +1092,14 @@ func TestSetJobScheduleWindow(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, "16:11 +0800", val)
 }
+
+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)
+}