diff --git a/vmm/src/config.rs b/vmm/src/config.rs
index 8a8d637fd..16089e558 100644
--- a/vmm/src/config.rs
+++ b/vmm/src/config.rs
@@ -1334,7 +1334,7 @@ impl FromStr for VhostMode {
 
 impl NetConfig {
     pub const SYNTAX: &'static str = "Network parameters \
-    \"tap=<if_name>,ip=<ip_addr>,mask=<net_mask>,mac=<mac_addr>,fd=<fd1,fd2...>,iommu=on|off,\
+    \"tap=<if_name>,ip=<ip_addr>,mask=<net_mask>,mac=<mac_addr>,fd=<[fd1,fd2,...]>,iommu=on|off,\
     num_queues=<number_of_queues>,queue_size=<size_of_each_queue>,id=<device_id>,\
     vhost_user=<vhost_user_enable>,socket=<vhost_user_socket_path>,vhost_mode=client|server,\
     bw_size=<bytes>,bw_one_time_burst=<bytes>,bw_refill_time=<ms>,\