diff --git a/src/bin/rnp/rnp_cli_options.rs b/src/bin/rnp/rnp_cli_options.rs
index 623648c..a0c698d 100644
--- a/src/bin/rnp/rnp_cli_options.rs
+++ b/src/bin/rnp/rnp_cli_options.rs
@@ -28,11 +28,11 @@ pub struct RnpCliOptions {
 
 #[derive(Debug, StructOpt, PartialEq)]
 pub struct RnpCliCommonOptions {
-    #[structopt(parse(try_from_str = parse_ping_target), help = "Target endpoint. For IPv6, please use [] to wrap the address, such as [::1]:80.")]
-    pub target: SocketAddr,
-
     #[structopt(short = "m", long = "mode", default_value = "TCP", help = "Specify protocol to use.")]
     pub protocol: RnpSupportedProtocol,
+
+    #[structopt(parse(try_from_str = parse_ping_target), help = "Target endpoint. For IPv6, please use [] to wrap the address, such as [::1]:80.")]
+    pub target: SocketAddr,
 }
 
 #[derive(Debug, StructOpt, PartialEq)]
diff --git a/src/ping_runners/ping_clients/ping_client_tcp.rs b/src/ping_runners/ping_clients/ping_client_tcp.rs
index 18fdafc..5ae357c 100644
--- a/src/ping_runners/ping_clients/ping_client_tcp.rs
+++ b/src/ping_runners/ping_clients/ping_client_tcp.rs
@@ -111,7 +111,7 @@ mod tests {
                 protocol: RnpSupportedProtocol::TCP,
                 server_address: "127.0.0.1:11337".parse().unwrap(),
                 close_on_accept: false,
-                sleep_before_write: Duration::from_millis(0),
+                sleep_before_write: Some(Duration::from_millis(0)),
                 write_chunk_size: 1024,
                 write_count_limit: Some(0),
                 report_interval: Duration::from_secs(1),
diff --git a/src/rnp_config.rs b/src/rnp_config.rs
index 1d1be96..a6cdf4f 100644
--- a/src/rnp_config.rs
+++ b/src/rnp_config.rs
@@ -174,7 +174,7 @@ pub struct RnpStubServerConfig {
     pub protocol: RnpSupportedProtocol,
     pub server_address: SocketAddr,
     pub close_on_accept: bool,
-    pub sleep_before_write: Duration,
+    pub sleep_before_write: Option<Duration>,
     pub write_chunk_size: usize,
     pub write_count_limit: Option<usize>,
     pub report_interval: Duration,
diff --git a/src/stub_servers/stub_server_tcp.rs b/src/stub_servers/stub_server_tcp.rs
index a747490..118e790 100644
--- a/src/stub_servers/stub_server_tcp.rs
+++ b/src/stub_servers/stub_server_tcp.rs
@@ -211,6 +211,10 @@ impl StubServerTcpConnection {
 
     #[tracing::instrument(name = "TCP connection on write", level = "debug", skip(self), fields(id = %self.id, remote_address = %self.remote_address))]
     async fn on_connection_write(&mut self) -> Result<(), Box<dyn Error>> {
+        if let Some(sleep_before_write) = self.config.sleep_before_write {
+            tokio::time::sleep(sleep_before_write).await;
+        }
+
         // Update write count
         {
             let mut conn_stats = self.conn_stats.lock().unwrap();