diff --git a/service/README.md b/service/README.md
index c77ee511..6ad0ccfe 100644
--- a/service/README.md
+++ b/service/README.md
@@ -29,6 +29,7 @@ Settings available in `local.conf` (this is not valid JSON, and JSON does not al
 		"secondaryPort": 1-65535, /* If set, override default random secondary port */
 		"tertiaryPort": 1-65535, /* If set, override default random tertiary port */
 		"portMappingEnabled": true|false, /* If true (the default), try to use uPnP or NAT-PMP to map ports */
+		"allowSecondaryPort": true|false /* false will also disable secondary port */
 		"softwareUpdate": "apply"|"download"|"disable", /* Automatically apply updates, just download, or disable built-in software updates */
 		"softwareUpdateChannel": "release"|"beta", /* Software update channel */
 		"softwareUpdateDist": true|false, /* If true, distribute software updates (only really useful to ZeroTier, Inc. itself, default is false) */