diff --git a/common/commonspace/synctree/queue.go b/common/commonspace/synctree/queue.go
new file mode 100644
index 00000000..3e71e1b8
--- /dev/null
+++ b/common/commonspace/synctree/queue.go
@@ -0,0 +1,66 @@
+package synctree
+
+import (
+	"errors"
+	"sync"
+)
+
+type ReceiveQueue interface {
+	AddMessage(senderId string, msg treeMsg) (queueFull bool)
+	GetMessage(senderId string) (msg treeMsg, err error)
+	ClearQueue(senderId string)
+}
+
+type receiveQueue struct {
+	sync.Mutex
+	handlerMap map[string][]treeMsg
+	maxSize    int
+}
+
+func newReceiveQueue(maxSize int) ReceiveQueue {
+	return &receiveQueue{
+		Mutex:      sync.Mutex{},
+		handlerMap: map[string][]treeMsg{},
+		maxSize:    maxSize,
+	}
+}
+
+var errEmptyQueue = errors.New("the queue is empty")
+
+func (q *receiveQueue) AddMessage(senderId string, msg treeMsg) (queueFull bool) {
+	q.Lock()
+	defer q.Unlock()
+
+	queue := q.handlerMap[senderId]
+	queueFull = len(queue) >= maxQueueSize
+	queue = append(queue, msg)
+	q.handlerMap[senderId] = queue
+
+	return
+}
+
+func (q *receiveQueue) GetMessage(senderId string) (msg treeMsg, err error) {
+	q.Lock()
+	defer q.Unlock()
+
+	if len(q.handlerMap) == 0 {
+		err = errEmptyQueue
+		return
+	}
+
+	msg = q.handlerMap[senderId][0]
+	return
+}
+
+func (q *receiveQueue) ClearQueue(senderId string) {
+	q.Lock()
+	defer q.Unlock()
+
+	queue := q.handlerMap[senderId]
+	excessLen := len(queue) - q.maxSize + 1
+	if excessLen <= 0 {
+		excessLen = 1
+	}
+	queue = queue[excessLen:]
+	q.handlerMap[senderId] = queue
+}
diff --git a/common/commonspace/synctree/synctreehandler.go b/common/commonspace/synctree/synctreehandler.go
index 8d97d5d2..77f17bc1 100644
--- a/common/commonspace/synctree/synctreehandler.go
+++ b/common/commonspace/synctree/synctreehandler.go
@@ -16,7 +16,7 @@ type syncTreeHandler struct {
 	objTree     tree.ObjectTree
 	syncClient  SyncClient
 	handlerLock sync.Mutex
-	handlerMap  map[string][]treeMsg
+	queue       ReceiveQueue
 }
 
 const maxQueueSize = 5
@@ -30,7 +30,7 @@ func newSyncTreeHandler(objTree tree.ObjectTree, syncClient SyncClient) synchand
 	return &syncTreeHandler{
 		objTree:    objTree,
 		syncClient: syncClient,
-		handlerMap: map[string][]treeMsg{},
+		queue:      newReceiveQueue(maxQueueSize),
 	}
 }
 
@@ -43,13 +43,7 @@ func (s *syncTreeHandler) HandleMessage(ctx context.Context, senderId string, ms
 		return
 	}
 
-	s.handlerLock.Lock()
-	queue := s.handlerMap[senderId]
-	queueFull := len(queue) >= maxQueueSize
-	queue = append(queue, treeMsg{msg.ReplyId, unmarshalled})
-	s.handlerMap[senderId] = queue
-	s.handlerLock.Unlock()
-
+	queueFull := s.queue.AddMessage(senderId, treeMsg{msg.ReplyId, unmarshalled})
 	if queueFull {
 		return
 	}
@@ -71,30 +65,19 @@ func (s *syncTreeHandler) HandleMessage(ctx context.Context, senderId string, ms
 func (s *syncTreeHandler) handleMessage(ctx context.Context, senderId string) (actions []sendFunc, err error) {
 	s.objTree.Lock()
 	defer s.objTree.Unlock()
-	s.handlerLock.Lock()
-	treeMessage := s.handlerMap[senderId][0]
-	unmarshalled := treeMessage.syncMessage
-	replyId := treeMessage.replyId
-	s.handlerLock.Unlock()
+	msg, err := s.queue.GetMessage(senderId)
+	if err != nil {
+		return
+	}
 
-	defer func() {
-		s.handlerLock.Lock()
-		defer s.handlerLock.Unlock()
-		queue := s.handlerMap[senderId]
-		excessLen := len(queue) - maxQueueSize + 1
-		if excessLen <= 0 {
-			excessLen = 1
-		}
-		queue = queue[excessLen:]
-		s.handlerMap[senderId] = queue
-	}()
+	defer s.queue.ClearQueue(senderId)
 
-	content := unmarshalled.GetContent()
+	content := msg.syncMessage.GetContent()
 	switch {
 	case content.GetHeadUpdate() != nil:
-		return s.handleHeadUpdate(ctx, senderId, content.GetHeadUpdate(), replyId)
+		return s.handleHeadUpdate(ctx, senderId, content.GetHeadUpdate(), msg.replyId)
 	case content.GetFullSyncRequest() != nil:
-		return s.handleFullSyncRequest(ctx, senderId, content.GetFullSyncRequest(), replyId)
+		return s.handleFullSyncRequest(ctx, senderId, content.GetFullSyncRequest(), msg.replyId)
 	case content.GetFullSyncResponse() != nil:
 		return s.handleFullSyncResponse(ctx, senderId, content.GetFullSyncResponse())
 	}