diff --git a/rpc/src/v1/impls/eth.rs b/rpc/src/v1/impls/eth.rs
index d8bcf9540..f90995ffe 100644
--- a/rpc/src/v1/impls/eth.rs
+++ b/rpc/src/v1/impls/eth.rs
@@ -118,7 +118,7 @@ impl Eth for EthClient {
 	// TODO: do not ignore block number param
 	fn code_at(&self, params: Params) -> Result<Value, Error> {
 		match from_params::<(Address, BlockNumber)>(params) {
-			Ok((address, _block_number)) => to_value(&Bytes::new(self.client.code(&address).unwrap_or_else(|| vec![]))),
+			Ok((address, _block_number)) => to_value(&self.client.code(&address).map_or_else(Bytes::default, Bytes::new)),
 			Err(err) => Err(err)
 		}
 	}
diff --git a/rpc/src/v1/mod.rs b/rpc/src/v1/mod.rs
index 11a5291b5..01635e872 100644
--- a/rpc/src/v1/mod.rs
+++ b/rpc/src/v1/mod.rs
@@ -21,6 +21,8 @@
 pub mod traits;
 mod impls;
 mod types;
+#[cfg(test)]
+mod tests;
 
 pub use self::traits::{Web3, Eth, EthFilter, Net};
 pub use self::impls::*;
diff --git a/rpc/src/v1/tests/mod.rs b/rpc/src/v1/tests/mod.rs
new file mode 100644
index 000000000..bdf4567b6
--- /dev/null
+++ b/rpc/src/v1/tests/mod.rs
@@ -0,0 +1 @@
+//TODO: load custom blockchain state and test
diff --git a/rpc/src/v1/types/bytes.rs b/rpc/src/v1/types/bytes.rs
index 51cb7f333..62aca8464 100644
--- a/rpc/src/v1/types/bytes.rs
+++ b/rpc/src/v1/types/bytes.rs
@@ -2,6 +2,7 @@ use rustc_serialize::hex::ToHex;
 use serde::{Serialize, Serializer};
 
 /// Wrapper structure around vector of bytes.
+#[derive(Debug)]
 pub struct Bytes(Vec<u8>);
 
 impl Bytes {
@@ -11,6 +12,13 @@ impl Bytes {
 	}
 }
 
+impl Default for Bytes {
+	fn default() -> Self {
+		// default serialized value is 0x00
+		Bytes(vec![0])
+	}
+}
+
 impl Serialize for Bytes {
 	fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error> 
 	where S: Serializer {
diff --git a/rpc/src/v1/types/mod.rs b/rpc/src/v1/types/mod.rs
index 0b8582910..226e7e9a6 100644
--- a/rpc/src/v1/types/mod.rs
+++ b/rpc/src/v1/types/mod.rs
@@ -18,8 +18,10 @@ mod block;
 mod block_number;
 mod bytes;
 mod sync;
+mod transaction;
 
 pub use self::block::Block;
 pub use self::block_number::BlockNumber;
 pub use self::bytes::Bytes;
 pub use self::sync::SyncStatus;
+pub use self::transaction::Transaction;
diff --git a/rpc/src/v1/types/transaction.rs b/rpc/src/v1/types/transaction.rs
new file mode 100644
index 000000000..de4490cbb
--- /dev/null
+++ b/rpc/src/v1/types/transaction.rs
@@ -0,0 +1,36 @@
+use util::hash::*;
+use util::uint::*;
+use v1::types::Bytes;
+
+#[derive(Debug, Default, Serialize)]
+pub struct Transaction {
+	hash: H256,
+	nonce: U256,
+	#[serde(rename="blockHash")]
+	block_hash: H256,
+	#[serde(rename="blockNumber")]
+	block_number: U256,
+	#[serde(rename="transactionIndex")]
+	transaction_index: U256,
+	from: Address,
+	to: Address,
+	value: U256,
+	#[serde(rename="gasPrice")]
+	gas_price: U256,
+	gas: U256,
+	input: Bytes
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use serde_json;
+
+	#[test]
+	fn test_transaction_serialize() {
+		let t = Transaction::default();
+		let serialized = serde_json::to_string(&t).unwrap();
+		assert_eq!(serialized, r#"{"hash":"0x0000000000000000000000000000000000000000000000000000000000000000","nonce":"0x00","blockHash":"0x0000000000000000000000000000000000000000000000000000000000000000","blockNumber":"0x00","transactionIndex":"0x00","from":"0x0000000000000000000000000000000000000000","to":"0x0000000000000000000000000000000000000000","value":"0x00","gasPrice":"0x00","gas":"0x00","input":"0x00"}"#);
+	}
+}
+
diff --git a/util/src/uint.rs b/util/src/uint.rs
index 4c0b533ef..b3427f6bc 100644
--- a/util/src/uint.rs
+++ b/util/src/uint.rs
@@ -458,7 +458,8 @@ macro_rules! construct_uint {
 				let mut hex = "0x".to_owned();
 				let mut bytes = [0u8; 8 * $n_words];
 				self.to_bytes(&mut bytes);
-				hex.push_str(bytes.to_hex().as_ref());
+				let len = cmp::max((self.bits() + 7) / 8, 1);
+				hex.push_str(bytes[bytes.len() - len..].to_hex().as_ref());
 				serializer.visit_str(hex.as_ref())
 			}
 		}