diff --git a/lib/session.js b/lib/session.js
index d38d7e0..dccb39b 100644
--- a/lib/session.js
+++ b/lib/session.js
@@ -662,9 +662,9 @@ Session.prototype.send = function (sender, tag, data, format) {
 };
 
 Session.prototype._write_flow = function (link) {
-    var fields = {'next_incoming_id':this.incoming.next_transfer_id,
+    var fields = {'next_incoming_id':this.incoming.next_transfer_id>>>0,
         'incoming_window':this.incoming.window,
-        'next_outgoing_id':this.outgoing.next_transfer_id,
+        'next_outgoing_id':this.outgoing.next_transfer_id>>>0,
         'outgoing_window':this.outgoing.window
     };
     this.incoming.max_transfer_id = fields.next_incoming_id + fields.incoming_window;