diff --git a/main.go b/main.go
index df97203..a5301ec 100644
--- a/main.go
+++ b/main.go
@@ -15,7 +15,7 @@ import (
 
 func main() {
 	dbFileArg := flag.String("dbfile", "./data.sqlite3", "File that holds the server's sqlite3 database. Will be created if it does not exist. Default is \"./data.sqlite3\".")
-	tilepackFileArg := flag.String("tilepack", "", "File that will be sent to clients when they request a tile pack. Required.")
+	tilepackFileArg := flag.String("tilepack", "", "File that will be sent to clients when they request a tile pack, also used to serve tiles in online mode. Required.")
 	apkFileArg := flag.String("apk", "", "APK file with the client app. If not specified, no APK will be available (404).")
 	reinitDBArg := flag.Bool("reinit-db", false, "Reinitializes the DB, which means all the tables will be recreated, deleting all data.")
 	minZoomArg := flag.Int("min-zoom", 1, "Minimum zoom that will be sent to clients.")