diff --git a/src/main/java/com/gzzn/omms/msgexchangeapi/service/FltrSendBufferService.java b/src/main/java/com/gzzn/omms/msgexchangeapi/service/FltrSendBufferService.java
index e6797a5c..f4678cca 100644
--- a/src/main/java/com/gzzn/omms/msgexchangeapi/service/FltrSendBufferService.java
+++ b/src/main/java/com/gzzn/omms/msgexchangeapi/service/FltrSendBufferService.java
@@ -21,7 +21,9 @@ public class FltrSendBufferService implements IFltrSendBufferService {
 	
 	@Override
 	public void addFltr(SCHD.FLTR  fltr) {
-		fltrBuffer.add(fltr);
+		synchronized (fltrBuffer) {
+		  fltrBuffer.add(fltr);
+		}
 	}