diff --git a/source/org/jivesoftware/smack/XMPPConnection.java b/source/org/jivesoftware/smack/XMPPConnection.java
index d04585081..9a65a8313 100644
--- a/source/org/jivesoftware/smack/XMPPConnection.java
+++ b/source/org/jivesoftware/smack/XMPPConnection.java
@@ -419,7 +419,7 @@ public class XMPPConnection extends Connection {
         saslAuthentication.init();
     }
 
-    public void disconnect(Presence unavailablePresence) {
+    public synchronized void disconnect(Presence unavailablePresence) {
         // If not connected, ignore this request.
         if (packetReader == null || packetWriter == null) {
             return;