--- a/master/mailbox.c	Thu Jul 09 12:54:49 2009 +0000
+++ b/master/mailbox.c	Thu Jul 09 14:05:36 2009 +0000
@@ -71,6 +71,7 @@
         return ERR_PTR(-EOVERFLOW);
     }
 
+    ec_datagram_zero(datagram);
     ret = ec_datagram_fpwr(datagram, slave->station_address,
             slave->configured_rx_mailbox_offset,
             slave->configured_rx_mailbox_size);