diff -r 0dc0873d4aed -r 524891614789 master/mailbox.c
--- a/master/mailbox.c	Wed Jun 22 13:49:16 2016 +0200
+++ b/master/mailbox.c	Wed Jun 22 13:50:35 2016 +0200
@@ -74,8 +74,9 @@
     ret = ec_datagram_fpwr(datagram, slave->station_address,
             slave->configured_rx_mailbox_offset,
             slave->configured_rx_mailbox_size);
-    if (ret)
+    if (ret) {
         return ERR_PTR(ret);
+    }
 
     EC_WRITE_U16(datagram->data,     size); // mailbox service data length
     EC_WRITE_U16(datagram->data + 2, slave->station_address); // station addr.