diff --git a/netrender/master_html.py b/netrender/master_html.py
index 877273207a84a28e896ccbd38d37c74fb06e5556..da9751841ad73db850d8720e989851852ccfab83 100644
--- a/netrender/master_html.py
+++ b/netrender/master_html.py
@@ -285,8 +285,9 @@ def get(handler):
                 headerTable("name", "address")
 
                 for slave_id in job.blacklist:
-                    slave = handler.server.slaves_map[slave_id]
-                    rowTable(slave.name, slave.address[0])
+                    slave = handler.server.slaves_map.get(slave_id, None)
+                    if slave:
+                        rowTable(slave.name, slave.address[0])
 
                 endTable()