diff --git a/contrib/tsn/model/cbs.cc b/contrib/tsn/model/cbs.cc
index cb0593d..b5a14ab 100644
--- a/contrib/tsn/model/cbs.cc
+++ b/contrib/tsn/model/cbs.cc
@@ -84,6 +84,10 @@ Cbs::Update()
     }
     else
     {
+      if (m_state == IDLE)
+      {
+      	UpdateCredit(false);
+      }
       m_state = WAITING;
     }
   }