diff --git a/bridges/relays/bin-substrate/src/cli/encode_call.rs b/bridges/relays/bin-substrate/src/cli/encode_call.rs
index 2d97c67800..1a2c8ebfb2 100644
--- a/bridges/relays/bin-substrate/src/cli/encode_call.rs
+++ b/bridges/relays/bin-substrate/src/cli/encode_call.rs
@@ -20,7 +20,7 @@ use relay_substrate_client::Chain;
 use structopt::{clap::arg_enum, StructOpt};
 
 /// Encode source chain runtime call.
-#[derive(StructOpt)]
+#[derive(StructOpt, Debug)]
 pub struct EncodeCall {
 	/// A bridge instance to encode call for.
 	#[structopt(possible_values = &EncodeCallBridge::variants(), case_insensitive = true)]
@@ -43,10 +43,10 @@ pub enum Call {
 	/// Make an on-chain remark (comment).
 	Remark {
 		/// Explicit remark payload.
-		#[structopt(long, conflicts_with("remark_size"))]
-		remark_payload: HexBytes,
+		#[structopt(long, conflicts_with("remark-size"))]
+		remark_payload: Option<HexBytes>,
 		/// Remark size. If not passed, small UTF8-encoded string is generated by relay as remark.
-		#[structopt(long, conflicts_with("remark_payload"))]
+		#[structopt(long, conflicts_with("remark-payload"))]
 		remark_size: Option<ExplicitOrMaximal<usize>>,
 	},
 	/// Transfer the specified `amount` of native tokens to a particular `recipient`.
@@ -165,11 +165,11 @@ pub(crate) fn preprocess_call<Source: CliEncodeCall + CliChain, Target: CliEncod
 			ref remark_size,
 			ref mut remark_payload,
 		} => {
-			if remark_payload.0.is_empty() {
-				*remark_payload = HexBytes(generate_remark_payload(
+			if remark_payload.is_none() {
+				*remark_payload = Some(HexBytes(generate_remark_payload(
 					&remark_size,
 					compute_maximal_message_arguments_size(Source::max_extrinsic_size(), Target::max_extrinsic_size()),
-				));
+				)));
 			}
 		}
 		Call::Transfer { ref mut recipient, .. } => {
@@ -246,4 +246,72 @@ mod tests {
 			"0x0c00d43593c715fdd31c61141abd04a99fd6822c8558854ccde39a5684e7a56da27de5c0"
 		);
 	}
+
+	#[test]
+	fn should_encode_remark_with_default_payload() {
+		// given
+		let mut encode_call = EncodeCall::from_iter(vec!["encode-call", "RialtoToMillau", "remark"]);
+
+		// when
+		let hex = encode_call.encode().unwrap();
+
+		// then
+		assert!(format!("{:?}", hex).starts_with("0x070154556e69782074696d653a"));
+	}
+
+	#[test]
+	fn should_encode_remark_with_explicit_payload() {
+		// given
+		let mut encode_call = EncodeCall::from_iter(vec![
+			"encode-call",
+			"RialtoToMillau",
+			"remark",
+			"--remark-payload",
+			"1234",
+		]);
+
+		// when
+		let hex = encode_call.encode().unwrap();
+
+		// then
+		assert_eq!(format!("{:?}", hex), "0x0701081234");
+	}
+
+	#[test]
+	fn should_encode_remark_with_size() {
+		// given
+		let mut encode_call =
+			EncodeCall::from_iter(vec!["encode-call", "RialtoToMillau", "remark", "--remark-size", "12"]);
+
+		// when
+		let hex = encode_call.encode().unwrap();
+
+		// then
+		assert_eq!(format!("{:?}", hex), "0x070130000000000000000000000000");
+	}
+
+	#[test]
+	fn should_disallow_both_payload_and_size() {
+		// when
+		let err = EncodeCall::from_iter_safe(vec![
+			"encode-call",
+			"RialtoToMillau",
+			"remark",
+			"--remark-payload",
+			"1234",
+			"--remark-size",
+			"12",
+		])
+		.unwrap_err();
+
+		// then
+		assert_eq!(err.kind, structopt::clap::ErrorKind::ArgumentConflict);
+		assert_eq!(
+			err.info,
+			Some(vec![
+				"remark-size".to_string(),
+				"--remark-payload <remark-payload>".to_string()
+			])
+		);
+	}
 }
diff --git a/bridges/relays/bin-substrate/src/rialto_millau/mod.rs b/bridges/relays/bin-substrate/src/rialto_millau/mod.rs
index 52f1d5201c..a39053aa4f 100644
--- a/bridges/relays/bin-substrate/src/rialto_millau/mod.rs
+++ b/bridges/relays/bin-substrate/src/rialto_millau/mod.rs
@@ -414,9 +414,9 @@ impl CliEncodeCall for Millau {
 	fn encode_call(call: &Call) -> anyhow::Result<Self::Call> {
 		Ok(match call {
 			Call::Raw { data } => Decode::decode(&mut &*data.0)?,
-			Call::Remark { remark_payload, .. } => {
-				millau_runtime::Call::System(millau_runtime::SystemCall::remark(remark_payload.0.clone()))
-			}
+			Call::Remark { remark_payload, .. } => millau_runtime::Call::System(millau_runtime::SystemCall::remark(
+				remark_payload.as_ref().map(|x| x.0.clone()).unwrap_or_default(),
+			)),
 			Call::Transfer { recipient, amount } => millau_runtime::Call::Balances(
 				millau_runtime::BalancesCall::transfer(recipient.raw_id(), amount.cast()),
 			),
@@ -487,9 +487,9 @@ impl CliEncodeCall for Rialto {
 	fn encode_call(call: &Call) -> anyhow::Result<Self::Call> {
 		Ok(match call {
 			Call::Raw { data } => Decode::decode(&mut &*data.0)?,
-			Call::Remark { remark_payload, .. } => {
-				rialto_runtime::Call::System(rialto_runtime::SystemCall::remark(remark_payload.0.clone()))
-			}
+			Call::Remark { remark_payload, .. } => rialto_runtime::Call::System(rialto_runtime::SystemCall::remark(
+				remark_payload.as_ref().map(|x| x.0.clone()).unwrap_or_default(),
+			)),
 			Call::Transfer { recipient, amount } => {
 				rialto_runtime::Call::Balances(rialto_runtime::BalancesCall::transfer(recipient.raw_id(), amount.0))
 			}