diff --git a/com/context.go b/com/context.go
index bfdcc98..3e9df19 100644
--- a/com/context.go
+++ b/com/context.go
@@ -12,12 +12,22 @@ import (
 var tlsIndex uint32
 
 type Context struct {
-	ID           int32 //could be reused
-	TID          uint32
-	CurrentScope *Scope
+	ID  int32 //could be reused
+	TID uint32
+
+	currentScope unsafe.Pointer // *Scope
 	LastError    *ErrorInfo
 }
 
+func (this *Context) GetCurrentScope() *Scope {
+	p := atomic.LoadPointer(&this.currentScope)
+	return (*Scope)(p)
+}
+
+func (this *Context) SetCurrentScope(s *Scope) {
+	atomic.StorePointer(&this.currentScope, unsafe.Pointer(s))
+}
+
 var contexts []*Context
 var muContext sync.Mutex
 
@@ -32,7 +42,6 @@ func init() {
 }
 
 func InitializeContext() {
-	//win32.TlsSetValue()
 	index := -1
 	context := &Context{}
 	context.TID = win32.GetCurrentThreadId()
@@ -110,9 +119,15 @@ func Initialize() Initialized {
 	InitializeContext()
 	win32.CoInitialize(nil)
 
-	//atomic.LoadInt32()
-	//tId := win32.GetCurrentThreadId()
-	//comThreadIds.Store(tId, true)
+	return Initialized{}
+}
+
+func InitializeMt() Initialized {
+	runtime.LockOSThread()
+
+	InitializeContext()
+	win32.CoInitializeEx(nil, win32.COINIT_MULTITHREADED)
+
 	return Initialized{}
 }
 
diff --git a/com/error.go b/com/error.go
index 3025d08..b1391db 100644
--- a/com/error.go
+++ b/com/error.go
@@ -29,6 +29,9 @@ func NewError(hr win32.HRESULT) Error {
 	return Error(hr)
 }
 
+const OK = Error(win32.S_OK)
+const FAIL = Error(win32.E_FAIL)
+
 func NewErrorOrNil(hr win32.HRESULT) error {
 	if win32.SUCCEEDED(hr) {
 		return nil
diff --git a/com/impl.go b/com/impl.go
index 30bade6..1e567de 100644
--- a/com/impl.go
+++ b/com/impl.go
@@ -176,6 +176,10 @@ type IUnknownComObj struct {
 	Parent   *IUnknownComObj
 }
 
+func (this *IUnknownComObj) GetIUnknown() *win32.IUnknown {
+	return this.IUnknown()
+}
+
 func (this *IUnknownComObj) AssignPpvObject(ppvObject unsafe.Pointer) {
 	*(*unsafe.Pointer)(ppvObject) = unsafe.Pointer(this)
 }
diff --git a/com/scope.go b/com/scope.go
index de6531e..44b63d7 100644
--- a/com/scope.go
+++ b/com/scope.go
@@ -3,6 +3,7 @@ package com
 import (
 	"github.com/zzl/go-win32api/win32"
 	"log"
+	"sync"
 	"unsafe"
 )
 
@@ -11,7 +12,7 @@ type scopedObject struct {
 	Type int //0:com interface, 1:bstr, 2:*variant, 3:safearray
 }
 
-//var CurrentScope *Scope
+var muScope sync.Mutex
 
 type Scope struct {
 	scopedObjs  []scopedObject
@@ -21,30 +22,36 @@ type Scope struct {
 func NewScope() *Scope {
 	context := GetContext()
 	scope := &Scope{
-		ParentScope: context.CurrentScope,
+		ParentScope: context.GetCurrentScope(),
 	}
-	context.CurrentScope = scope
+	context.SetCurrentScope(scope)
 	return scope
 }
 
+func (this *Scope) _add(so scopedObject) {
+	muScope.Lock()
+	this.scopedObjs = append(this.scopedObjs, so)
+	muScope.Unlock()
+}
+
 func (this *Scope) Add(pUnknown unsafe.Pointer) {
-	this.scopedObjs = append(this.scopedObjs, scopedObject{Ptr: pUnknown})
+	this._add(scopedObject{Ptr: pUnknown})
 }
 
 func (this *Scope) AddComPtr(iunknownObj win32.IUnknownObject, addRef ...bool) {
 	pUnknown := iunknownObj.GetIUnknown()
-	this.scopedObjs = append(this.scopedObjs, scopedObject{Ptr: unsafe.Pointer(pUnknown), Type: 0})
 	if len(addRef) == 1 && addRef[0] {
 		pUnknown.AddRef()
 	}
+	this._add(scopedObject{Ptr: unsafe.Pointer(pUnknown), Type: 0})
 }
 
 func (this *Scope) AddBstr(bstr win32.BSTR) {
-	this.scopedObjs = append(this.scopedObjs, scopedObject{Ptr: unsafe.Pointer(bstr), Type: 1})
+	this._add(scopedObject{Ptr: unsafe.Pointer(bstr), Type: 1})
 }
 
 func (this *Scope) AddVar(pVar *win32.VARIANT) {
-	this.scopedObjs = append(this.scopedObjs, scopedObject{Ptr: unsafe.Pointer(pVar), Type: 2})
+	this._add(scopedObject{Ptr: unsafe.Pointer(pVar), Type: 2})
 }
 
 func (this *Scope) AddVarIfNeeded(pVar *win32.VARIANT) {
@@ -54,11 +61,11 @@ func (this *Scope) AddVarIfNeeded(pVar *win32.VARIANT) {
 	default:
 		return
 	}
-	this.scopedObjs = append(this.scopedObjs, scopedObject{Ptr: unsafe.Pointer(pVar), Type: 2})
+	this._add(scopedObject{Ptr: unsafe.Pointer(pVar), Type: 2})
 }
 
 func (this *Scope) AddArray(psa *win32.SAFEARRAY) {
-	this.scopedObjs = append(this.scopedObjs, scopedObject{Ptr: unsafe.Pointer(psa), Type: 3})
+	this._add(scopedObject{Ptr: unsafe.Pointer(psa), Type: 3})
 }
 
 type VariantCompatible interface {
@@ -70,7 +77,7 @@ func AddToScope(value interface{}, scope ...*Scope) {
 	if len(scope) != 0 {
 		s = scope[0]
 	} else {
-		currentScope := GetContext().CurrentScope
+		currentScope := GetContext().GetCurrentScope()
 		if currentScope == nil {
 			log.Panic("no current scope")
 		}
@@ -104,13 +111,19 @@ func WithScope(action func()) {
 
 func (this *Scope) Leave() {
 	this.Clear()
-	GetContext().CurrentScope = this.ParentScope
+	GetContext().SetCurrentScope(this.ParentScope)
 }
 
 func (this *Scope) Clear() {
+	muScope.Lock()
 	count := len(this.scopedObjs)
-	for n := 0; n < count; n++ {
-		obj := this.scopedObjs[n]
+	scopedObjs := make([]scopedObject, count)
+	copy(scopedObjs, this.scopedObjs)
+	this.scopedObjs = nil
+	muScope.Unlock()
+
+	for n := count - 1; n >= 0; n-- {
+		obj := scopedObjs[n]
 		if obj.Type == 0 {
 			(*win32.IUnknown)(obj.Ptr).Release()
 		} else if obj.Type == 1 {
@@ -121,5 +134,5 @@ func (this *Scope) Clear() {
 			win32.SafeArrayDestroy((*win32.SAFEARRAY)(obj.Ptr))
 		}
 	}
-	this.scopedObjs = nil
+
 }
diff --git a/go.mod b/go.mod
index 7e2d87d..c81c862 100644
--- a/go.mod
+++ b/go.mod
@@ -2,8 +2,6 @@ module github.com/zzl/go-com
 
 go 1.18
 
-replace github.com/zzl/go-win32api v1.1.3 => C:\Users\zzl\Documents\GitHub\go-win32api
-
-require github.com/zzl/go-win32api v1.1.3
+require github.com/zzl/go-win32api v1.2.0
 
 require golang.org/x/sys v0.0.0-20220330033206-e17cdc41300f // indirect
diff --git a/go.sum b/go.sum
index 669aa19..857f8c3 100644
--- a/go.sum
+++ b/go.sum
@@ -1,2 +1,4 @@
+github.com/zzl/go-win32api v1.2.0 h1:8cUPn/io9S0H/Ah4pnuM7xmElL2MDR9bKgl8AREG/AE=
+github.com/zzl/go-win32api v1.2.0/go.mod h1:iWVjU/KzuwzqGpgBZdQ6Z4JqFXeSPIzantVIkcyD4b4=
 golang.org/x/sys v0.0.0-20220330033206-e17cdc41300f h1:rlezHXNlxYWvBCzNses9Dlc7nGFaNMJeqLolcmQSSZY=
 golang.org/x/sys v0.0.0-20220330033206-e17cdc41300f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
diff --git a/ole/oleclient.go b/ole/oleclient.go
index 90c37e0..df0c98d 100644
--- a/ole/oleclient.go
+++ b/ole/oleclient.go
@@ -161,8 +161,7 @@ func SetVariantParam(v *Variant, value interface{}, unwrapActions *Actions) {
 		*v.PvarVal() = (*win32.VARIANT)(val)
 	case int8:
 		v.Vt = uint16(win32.VT_I1)
-		//*v.CVal() = win32.CHAR(val)
-		*v.CVal() = val
+		*v.CVal() = win32.CHAR(val)
 	case uint8:
 		v.Vt = uint16(win32.VT_UI1)
 		*v.BVal() = val
@@ -202,8 +201,7 @@ func SetVariantParam(v *Variant, value interface{}, unwrapActions *Actions) {
 		})
 	case *int8:
 		v.Vt = uint16(win32.VT_I1 | win32.VT_BYREF)
-		//*v.PcVal() = (*win32.CHAR)(unsafe.Pointer(val))
-		*v.PcVal() = val
+		*v.PcVal() = (*win32.CHAR)(unsafe.Pointer(val))
 	case *uint8:
 		v.Vt = uint16(win32.VT_UI1 | win32.VT_BYREF)
 		*v.PbVal() = val
diff --git a/ole/variant.go b/ole/variant.go
index d6ca0b0..b74d060 100644
--- a/ole/variant.go
+++ b/ole/variant.go
@@ -58,8 +58,7 @@ func NewVariant(value interface{}) *Variant {
 	case int8:
 		v := &Variant{}
 		v.Vt = uint16(win32.VT_I1)
-		//*v.CVal() = win32.CHAR(val)
-		*v.CVal() = val
+		*v.CVal() = win32.CHAR(val)
 		return v
 	case uint8:
 		v := &Variant{}