diff --git a/README.md b/README.md
index e9fe36b502..775bc47408 100644
--- a/README.md
+++ b/README.md
@@ -21,11 +21,16 @@ Once that finishes, you can run the development server as follows:
   # Now inside the container
   cd /srv/zulip
   source /srv/zulip-venv/bin/activate
-  ./tools/run-dev.py
+  ./tools/run-dev.py --interface=''
 
 You can now visit <http://localhost:9991/> in your browser.  To get
 shell access to the virtual machine running the server, use `vagrant ssh`.
 
+(A small note on tools/run-dev.py: the --interface='' option will make
+the development server listen on all network interfaces.  While this
+is correct for the Vagrant guest sitting behind a NAT, you probably
+don't want to use that option when using run-dev.py in other environments).
+
 The run-dev.py console output will show any errors your Zulip
 development server encounters.  It runs on top of Django's "manage.py
 runserver" tool, which will automatically restart the Zulip server