diff --git a/src/lib.rs b/src/lib.rs
index f95bbf01d..df2e7c528 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,22 +2,20 @@
 extern crate ethcore_util;
 
 use ethcore_util::hash::*;
+use ethcore_util::uint::*;
 
 pub type Bytes = Vec<u8>;
-pub type Uint256 = Hash256;
 pub type LogBloom = Hash4096;
 
-pub const ZERO_UINT256: Uint256 = Hash256([0x00; 32]);
-pub const ZERO_ADDRESS: Address = Address([0x00; 20]);
-pub const BAD_UINT256: Uint256 = Hash256([0xff; 32]);
-pub const ZERO_HASH256: Hash256 = Hash256([0x00; 32]);
-pub const ZERO_LOGBLOOM: LogBloom = Hash4096([0x00; 512]);
+pub static ZERO_ADDRESS: Address = Address([0x00; 20]);
+pub static ZERO_HASH256: Hash256 = Hash256([0x00; 32]);
+pub static ZERO_LOGBLOOM: LogBloom = Hash4096([0x00; 512]);
 
 #[derive(Debug)]
 pub struct Header {
 	parent_hash: Hash256,
-	timestamp: Uint256,
-	number: Uint256,
+	timestamp: U256,
+	number: U256,
 	author: Address,
 
 	transactions_root: Hash256,
@@ -27,19 +25,19 @@ pub struct Header {
 	state_root: Hash256,
 	receipts_root: Hash256,
 	log_bloom: LogBloom,
-	gas_used: Uint256,
-	gas_limit: Uint256,
+	gas_used: U256,
+	gas_limit: U256,
 
-	difficulty: Uint256,
+	difficulty: U256,
 	seal: Vec<Bytes>,
 }
 
 impl Header {
 	pub fn new() -> Header {
 		Header {
-			parent_hash: ZERO_UINT256,
-			timestamp: BAD_UINT256,
-			number: ZERO_UINT256,
+			parent_hash: ZERO_HASH256,
+			timestamp: BAD_U256,
+			number: ZERO_U256,
 			author: ZERO_ADDRESS,
 
 			transactions_root: ZERO_HASH256,
@@ -49,10 +47,10 @@ impl Header {
 			state_root: ZERO_HASH256,
 			receipts_root: ZERO_HASH256,
 			log_bloom: ZERO_LOGBLOOM,
-			gas_used: ZERO_UINT256,
-			gas_limit: ZERO_UINT256,
+			gas_used: ZERO_U256,
+			gas_limit: ZERO_U256,
 
-			difficulty: ZERO_UINT256,
+			difficulty: ZERO_U256,
 			seal: vec![],
 		}
 	}
@@ -60,7 +58,7 @@ impl Header {
 
 pub struct Transaction {
 	pub to: Address,
-	pub gas: Uint256,
+	pub gas: U256,
 	pub data: Bytes,
 	pub code: Bytes,
 }