diff --git a/docs/source/index.rst b/docs/source/index.rst
index 4cd9d46..5c2ebf2 100644
--- a/docs/source/index.rst
+++ b/docs/source/index.rst
@@ -147,6 +147,8 @@
            Setting this flag will cause BBSim to not store data like traffic schedulers, flows of ONUs etc
      -kafkaEventTopic string
            Set the topic on which BBSim publishes events on kafka
+     -igmp
+           Set this flag to start IGMP automatically
 
 ``BBSim`` also looks for a configuration file in ``configs/bbsim.yaml`` from
 which it reads a number of default settings. The command line options listed