diff --git a/rpc/src/v1/impls/signing.rs b/rpc/src/v1/impls/signing.rs
index 4ee44bb26..5fc6558da 100644
--- a/rpc/src/v1/impls/signing.rs
+++ b/rpc/src/v1/impls/signing.rs
@@ -18,7 +18,7 @@
 
 use std::sync::{Arc, Weak};
 use transient_hashmap::TransientHashMap;
-use util::{U256, Mutex};
+use util::{U256, Mutex, Hashable};
 
 use ethcore::account_provider::AccountProvider;
 use ethcore::miner::MinerService;
@@ -180,7 +180,8 @@ impl<C: 'static, M: 'static> EthSigning for SigningQueueClient<C, M> where
 	C: MiningBlockChainClient,
 	M: MinerService,
 {
-	fn sign(&self, ready: Ready<RpcH520>, address: RpcH160, hash: RpcH256) {
+	fn sign(&self, ready: Ready<RpcH520>, address: RpcH160, data: RpcBytes) {
+		let hash = data.0.sha3().into();
 		let res = self.active().and_then(|_| self.dispatch(RpcConfirmationPayload::Signature((address, hash).into())));
 		self.handle_dispatch(res, |response| {
 			match response {
diff --git a/rpc/src/v1/impls/signing_unsafe.rs b/rpc/src/v1/impls/signing_unsafe.rs
index 992bb85b0..2b3b81d57 100644
--- a/rpc/src/v1/impls/signing_unsafe.rs
+++ b/rpc/src/v1/impls/signing_unsafe.rs
@@ -17,6 +17,7 @@
 //! Unsafe Signing RPC implementation.
 
 use std::sync::{Arc, Weak};
+use util::Hashable;
 
 use ethcore::account_provider::AccountProvider;
 use ethcore::miner::MinerService;
@@ -83,7 +84,8 @@ impl<C: 'static, M: 'static> EthSigning for SigningUnsafeClient<C, M> where
 	C: MiningBlockChainClient,
 	M: MinerService,
 {
-	fn sign(&self, ready: Ready<RpcH520>, address: RpcH160, hash: RpcH256) {
+	fn sign(&self, ready: Ready<RpcH520>, address: RpcH160, data: RpcBytes) {
+		let hash = data.0.sha3().into();
 		let result = match self.handle(RpcConfirmationPayload::Signature((address, hash).into())) {
 			Ok(RpcConfirmationResponse::Signature(signature)) => Ok(signature),
 			Err(e) => Err(e),
diff --git a/rpc/src/v1/tests/mocked/eth.rs b/rpc/src/v1/tests/mocked/eth.rs
index f84f4d53e..ea8409ef2 100644
--- a/rpc/src/v1/tests/mocked/eth.rs
+++ b/rpc/src/v1/tests/mocked/eth.rs
@@ -18,11 +18,11 @@ use std::str::FromStr;
 use std::collections::HashMap;
 use std::sync::Arc;
 use std::time::{Instant, Duration};
-use rustc_serialize::hex::ToHex;
+use rustc_serialize::hex::{FromHex, ToHex};
 use time::get_time;
 use rlp;
 
-use util::{Uint, U256, Address, H256, FixedHash, Mutex};
+use util::{Uint, U256, Address, H256, FixedHash, Mutex, Hashable};
 use ethcore::account_provider::AccountProvider;
 use ethcore::client::{TestBlockChainClient, EachBlockWith, Executed, TransactionId};
 use ethcore::log_entry::{LocalizedLogEntry, LogEntry};
@@ -294,8 +294,8 @@ fn rpc_eth_sign() {
 
 	let account = tester.accounts_provider.new_account("abcd").unwrap();
 	tester.accounts_provider.unlock_account_permanently(account, "abcd".into()).unwrap();
-	let message = H256::from("0x0cc175b9c0f1b6a831c399e26977266192eb5ffee6ae2fec3ad71c777531578f");
-	let signed = tester.accounts_provider.sign(account, None, message).unwrap();
+	let message = "0cc175b9c0f1b6a831c399e26977266192eb5ffee6ae2fec3ad71c777531578f".from_hex().unwrap();
+	let signed = tester.accounts_provider.sign(account, None, message.sha3()).unwrap();
 
 	let req = r#"{
 		"jsonrpc": "2.0",
diff --git a/rpc/src/v1/tests/mocked/signing.rs b/rpc/src/v1/tests/mocked/signing.rs
index 526360f0f..5217ad402 100644
--- a/rpc/src/v1/tests/mocked/signing.rs
+++ b/rpc/src/v1/tests/mocked/signing.rs
@@ -26,7 +26,7 @@ use v1::types::ConfirmationResponse;
 use v1::tests::helpers::TestMinerService;
 use v1::tests::mocked::parity;
 
-use util::{Address, FixedHash, Uint, U256, H256, ToPretty};
+use util::{Address, FixedHash, Uint, U256, ToPretty, Hashable};
 use ethcore::account_provider::AccountProvider;
 use ethcore::client::TestBlockChainClient;
 use ethcore::transaction::{Transaction, Action};
@@ -186,11 +186,11 @@ fn should_check_status_of_request_when_its_resolved() {
 fn should_sign_if_account_is_unlocked() {
 	// given
 	let tester = eth_signing();
-	let hash: H256 = 5.into();
+	let data = vec![5u8];
 	let acc = tester.accounts.new_account("test").unwrap();
 	tester.accounts.unlock_account_permanently(acc, "test".into()).unwrap();
 
-	let signature = tester.accounts.sign(acc, None, hash).unwrap();
+	let signature = tester.accounts.sign(acc, None, data.sha3()).unwrap();
 
 	// when
 	let request = r#"{
@@ -198,7 +198,7 @@ fn should_sign_if_account_is_unlocked() {
 		"method": "eth_sign",
 		"params": [
 			""#.to_owned() + format!("0x{:?}", acc).as_ref() + r#"",
-			""# + format!("0x{:?}", hash).as_ref() + r#""
+			""# + format!("0x{}", data.to_hex()).as_ref() + r#""
 		],
 		"id": 1
 	}"#;
diff --git a/rpc/src/v1/traits/eth_signing.rs b/rpc/src/v1/traits/eth_signing.rs
index 4f8dc5b1b..aa306f3f0 100644
--- a/rpc/src/v1/traits/eth_signing.rs
+++ b/rpc/src/v1/traits/eth_signing.rs
@@ -17,14 +17,14 @@
 //! Eth rpc interface.
 
 use v1::helpers::auto_args::{WrapAsync, Ready};
-use v1::types::{H160, H256, H520, TransactionRequest, RichRawTransaction};
+use v1::types::{Bytes, H160, H256, H520, TransactionRequest, RichRawTransaction};
 
 build_rpc_trait! {
 	/// Signing methods implementation relying on unlocked accounts.
 	pub trait EthSigning {
-		/// Signs the data with given address signature.
+		/// Signs the hash of data with given address signature.
 		#[rpc(async, name = "eth_sign")]
-		fn sign(&self, Ready<H520>, H160, H256);
+		fn sign(&self, Ready<H520>, H160, Bytes);
 
 		/// Sends transaction; will block waiting for signer to return the
 		/// transaction hash.