diff --git a/config/zabbix_agentd/zabbix_agentd.conf b/config/zabbix_agentd/zabbix_agentd.conf
index 4480e43f2..a5a608d83 100644
--- a/config/zabbix_agentd/zabbix_agentd.conf
+++ b/config/zabbix_agentd/zabbix_agentd.conf
@@ -13,7 +13,16 @@
 Server=127.0.0.1
 ServerActive=127.0.0.1
 
-# List of comma delimited IP addresses that the agent should listen on.
+# Number of pre-forked instances of zabbix_agentd that process passive checks.
+# On IPFire this is set to 0 to disable passive checks and only allow active
+# checks by default.
+# Set this value in a range of 1-100 to enable passive checks or comment it
+# out to revert to the Zabbix agent default (10).
+StartAgents=0
+
+# List of comma delimited IP addresses that the agent should listen on
+# for passive checks. 
+# The agent will not listen on any TCP port when StartAgents is set to 0.
 ListenIP=GREEN_ADDRESS
 
 # This line activates IPFire specific userparameters.