diff --git a/src/sync/src/syncMain.c b/src/sync/src/syncMain.c
index e70e27b0efbb22c76b9044eec99d831eff94b62e..04e402769b513a269ac3c5a23d64e92318932bc4 100644
--- a/src/sync/src/syncMain.c
+++ b/src/sync/src/syncMain.c
@@ -537,7 +537,8 @@ static void syncResetFlowCtrl(SSyncNode *pNode) {
     pNode->peerInfo[i]->numOfRetrieves = 0;
   }
 
-  (*pNode->notifyFlowCtrl)(pNode->ahandle, 0);   
+  if (pNode->notifyFlowCtrl)
+    (*pNode->notifyFlowCtrl)(pNode->ahandle, 0);   
 }
 
 static void syncChooseMaster(SSyncNode *pNode) {
diff --git a/src/sync/src/syncRetrieve.c b/src/sync/src/syncRetrieve.c
index be3a3c2ac7b20e75aee1fea871bc6ae11f74d5a9..7bd97f5abec4204658d83b9f905cbf9dd902e63c 100644
--- a/src/sync/src/syncRetrieve.c
+++ b/src/sync/src/syncRetrieve.c
@@ -477,11 +477,12 @@ void *syncRetrieveData(void *param)
   if (pPeer->fileChanged) {
     // if file is changed 3 times continuously, start flow control
     pPeer->numOfRetrieves++;
-    if (pPeer->numOfRetrieves >= 3) 
+    if (pPeer->numOfRetrieves >= 3 && pNode->notifyFlowCtrl)  
       (*pNode->notifyFlowCtrl)(pNode->ahandle, pPeer->numOfRetrieves - 2);
   } else {
     pPeer->numOfRetrieves = 0;
-    (*pNode->notifyFlowCtrl)(pNode->ahandle, 0);
+    if (pNode->notifyFlowCtrl)
+      (*pNode->notifyFlowCtrl)(pNode->ahandle, 0);
   }
 
   pPeer->fileChanged = 0;