--- a/linux-2.6-xen-sparse/drivers/xen/netback/netback.c	2006-10-26 08:46:06.000000000 -0600
+++ b/linux-2.6-xen-sparse/drivers/xen/netback/netback.c	2006-11-06 10:26:24.000000000 -0700
@@ -815,6 +815,7 @@
 static void tx_add_credit(netif_t *netif)
 {
 	unsigned long max_burst;
+	unsigned long max_credit;
 
 	/*
 	 * Allow a burst big enough to transmit a jumbo packet of up to 128kB.
@@ -823,10 +824,10 @@
 	max_burst = RING_GET_REQUEST(&netif->tx, netif->tx.req_cons)->size;
 	max_burst = min(max_burst, 131072UL);
 	max_burst = max(max_burst, netif->credit_bytes);
+	max_credit = max(netif->remaining_credit + netif->credit_bytes,
+		netif->credit_bytes);
 
-	netif->remaining_credit = min(netif->remaining_credit +
-				      netif->credit_bytes,
-				      max_burst);
+	netif->remaining_credit = min(max_credit, max_burst);
 }
 
 static void tx_credit_callback(unsigned long data)