diff --git a/ethcore/src/client/test_client.rs b/ethcore/src/client/test_client.rs
index 621f880c5..812c15655 100644
--- a/ethcore/src/client/test_client.rs
+++ b/ethcore/src/client/test_client.rs
@@ -29,6 +29,7 @@ use blockchain::extras::BlockReceipts;
 use error::{ImportResult};
 use evm::Factory as EvmFactory;
 use miner::{Miner, MinerService};
+use spec::Spec;
 
 use block_queue::BlockQueueInfo;
 use block::OpenBlock;
@@ -105,7 +106,7 @@ impl TestBlockChainClient {
 			execution_result: RwLock::new(None),
 			receipts: RwLock::new(HashMap::new()),
 			queue_size: AtomicUsize::new(0),
-			miner: Arc::new(Miner::default()),
+			miner: Arc::new(Miner::with_spec(Spec::new_test())),
 		};
 		client.add_blocks(1, EachBlockWith::Nothing); // add genesis block
 		client.genesis_hash = client.last_hash.read().unwrap().clone();
diff --git a/ethcore/src/json_tests/chain.rs b/ethcore/src/json_tests/chain.rs
index 2bee5eb2a..c8e967d76 100644
--- a/ethcore/src/json_tests/chain.rs
+++ b/ethcore/src/json_tests/chain.rs
@@ -22,6 +22,7 @@ use tests::helpers::*;
 use devtools::*;
 use spec::Genesis;
 use ethjson;
+use ethjson::blockchain::BlockChain;
 use miner::Miner;
 
 pub fn json_chain_test(json_data: &[u8], era: ChainEra) -> Vec<String> {
@@ -41,20 +42,28 @@ pub fn json_chain_test(json_data: &[u8], era: ChainEra) -> Vec<String> {
 
 			flush!("   - {}...", name);
 
-			let mut spec = match era {
-				ChainEra::Frontier => ethereum::new_frontier_test(),
-				ChainEra::Homestead => ethereum::new_homestead_test(),
+			let spec = |blockchain: &BlockChain| {
+				let genesis = Genesis::from(blockchain.genesis());
+				let state = From::from(blockchain.pre_state.clone());
+				let mut spec = match era {
+					ChainEra::Frontier => ethereum::new_frontier_test(),
+					ChainEra::Homestead => ethereum::new_homestead_test(),
+				};
+				spec.set_genesis_state(state);
+				spec.overwrite_genesis_params(genesis);
+				assert!(spec.is_state_root_valid());
+				spec
 			};
 
-			let genesis = Genesis::from(blockchain.genesis());
-			let state = From::from(blockchain.pre_state.clone());
-			spec.set_genesis_state(state);
-			spec.overwrite_genesis_params(genesis);
-			assert!(spec.is_state_root_valid());
-
 			let temp = RandomTempPath::new();
 			{
-				let client = Client::new(ClientConfig::default(), spec, temp.as_path(), Arc::new(Miner::default()), IoChannel::disconnected()).unwrap();
+				let client = Client::new(
+					ClientConfig::default(),
+					spec(&blockchain),
+					temp.as_path(),
+					Arc::new(Miner::with_spec(spec(&blockchain))),
+					IoChannel::disconnected()
+				).unwrap();
 				for b in &blockchain.blocks_rlp() {
 					if Block::is_good(&b) {
 						let _ = client.import_block(b.clone());
diff --git a/ethcore/src/miner/miner.rs b/ethcore/src/miner/miner.rs
index 709a32482..401a5314a 100644
--- a/ethcore/src/miner/miner.rs
+++ b/ethcore/src/miner/miner.rs
@@ -47,8 +47,9 @@ pub struct Miner {
 	accounts: Option<Arc<AccountProvider>>,
 }
 
-impl Default for Miner {
-	fn default() -> Miner {
+impl Miner {
+	/// Creates new instance of miner without accounts, but with given spec.
+	pub fn with_spec(spec: Spec) -> Miner {
 		Miner {
 			transaction_queue: Mutex::new(TransactionQueue::new()),
 			force_sealing: false,
@@ -59,14 +60,12 @@ impl Default for Miner {
 			author: RwLock::new(Address::default()),
 			extra_data: RwLock::new(Vec::new()),
 			accounts: None,
-			spec: Spec::new_test(),
+			spec: spec,
 		}
 	}
-}
 
-impl Miner {
 	/// Creates new instance of miner
-	pub fn new(force_sealing: bool, spec: Spec) -> Arc<Miner> {
+	pub fn new(force_sealing: bool, spec: Spec, accounts: Option<Arc<AccountProvider>>) -> Arc<Miner> {
 		Arc::new(Miner {
 			transaction_queue: Mutex::new(TransactionQueue::new()),
 			force_sealing: force_sealing,
@@ -76,23 +75,7 @@ impl Miner {
 			gas_range_target: RwLock::new((U256::zero(), U256::zero())),
 			author: RwLock::new(Address::default()),
 			extra_data: RwLock::new(Vec::new()),
-			accounts: None,
-			spec: spec,
-		})
-	}
-
-	/// Creates new instance of miner
-	pub fn with_accounts(force_sealing: bool, spec: Spec, accounts: Arc<AccountProvider>) -> Arc<Miner> {
-		Arc::new(Miner {
-			transaction_queue: Mutex::new(TransactionQueue::new()),
-			force_sealing: force_sealing,
-			sealing_enabled: AtomicBool::new(force_sealing),
-			sealing_block_last_request: Mutex::new(0),
-			sealing_work: Mutex::new(UsingQueue::new(5)),
-			gas_range_target: RwLock::new((U256::zero(), U256::zero())),
-			author: RwLock::new(Address::default()),
-			extra_data: RwLock::new(Vec::new()),
-			accounts: Some(accounts),
+			accounts: accounts,
 			spec: spec,
 		})
 	}
@@ -626,6 +609,7 @@ mod tests {
 	use util::*;
 	use client::{TestBlockChainClient, EachBlockWith};
 	use block::*;
+	use spec::Spec;
 
 	// TODO [ToDr] To uncomment` when TestBlockChainClient can actually return a ClosedBlock.
 	#[ignore]
@@ -633,7 +617,7 @@ mod tests {
 	fn should_prepare_block_to_seal() {
 		// given
 		let client = TestBlockChainClient::default();
-		let miner = Miner::default();
+		let miner = Miner::with_spec(Spec::new_test());
 
 		// when
 		let sealing_work = miner.map_sealing_work(&client, |_| ());
@@ -645,7 +629,7 @@ mod tests {
 	fn should_still_work_after_a_couple_of_blocks() {
 		// given
 		let client = TestBlockChainClient::default();
-		let miner = Miner::default();
+		let miner = Miner::with_spec(Spec::new_test());
 
 		let res = miner.map_sealing_work(&client, |b| b.block().fields().header.hash());
 		assert!(res.is_some());
diff --git a/ethcore/src/miner/mod.rs b/ethcore/src/miner/mod.rs
index b28dcbe8d..6e415a602 100644
--- a/ethcore/src/miner/mod.rs
+++ b/ethcore/src/miner/mod.rs
@@ -28,11 +28,12 @@
 //! extern crate ethcore;
 //! use std::env;
 //! use util::network::{NetworkService, NetworkConfiguration};
+//! use ethcore::ethereum;
 //! use ethcore::client::{Client, ClientConfig};
 //! use ethcore::miner::{Miner, MinerService};
 //!
 //! fn main() {
-//!		let miner: Miner = Miner::default();
+//!		let miner: Miner = Miner::with_spec(ethereum::new_frontier(true));
 //!		// get status
 //!		assert_eq!(miner.status().transactions_in_pending_queue, 0);
 //!
diff --git a/ethcore/src/service.rs b/ethcore/src/service.rs
index 03a85ce13..98fb3ad23 100644
--- a/ethcore/src/service.rs
+++ b/ethcore/src/service.rs
@@ -159,9 +159,15 @@ mod tests {
 
 	#[test]
 	fn it_can_be_started() {
-		let spec = get_test_spec();
 		let temp_path = RandomTempPath::new();
-		let service = ClientService::start(ClientConfig::default(), spec, NetworkConfiguration::new_local(), &temp_path.as_path(), Arc::new(Miner::default()), false);
+		let service = ClientService::start(
+			ClientConfig::default(),
+			get_test_spec(),
+			NetworkConfiguration::new_local(),
+			&temp_path.as_path(),
+			Arc::new(Miner::with_spec(get_test_spec())),
+			false
+		);
 		assert!(service.is_ok());
 	}
 }
diff --git a/ethcore/src/tests/client.rs b/ethcore/src/tests/client.rs
index 79ffa7147..63302cb30 100644
--- a/ethcore/src/tests/client.rs
+++ b/ethcore/src/tests/client.rs
@@ -24,7 +24,7 @@ use miner::Miner;
 #[test]
 fn imports_from_empty() {
 	let dir = RandomTempPath::new();
-	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), Arc::new(Miner::default()), IoChannel::disconnected()).unwrap();
+	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), Arc::new(Miner::with_spec(get_test_spec())), IoChannel::disconnected()).unwrap();
 	client.import_verified_blocks(&IoChannel::disconnected());
 	client.flush_queue();
 }
@@ -42,7 +42,7 @@ fn returns_state_root_basic() {
 #[test]
 fn imports_good_block() {
 	let dir = RandomTempPath::new();
-	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), Arc::new(Miner::default()), IoChannel::disconnected()).unwrap();
+	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), Arc::new(Miner::with_spec(get_test_spec())), IoChannel::disconnected()).unwrap();
 	let good_block = get_good_dummy_block();
 	if let Err(_) = client.import_block(good_block) {
 		panic!("error importing block being good by definition");
@@ -57,7 +57,7 @@ fn imports_good_block() {
 #[test]
 fn query_none_block() {
 	let dir = RandomTempPath::new();
-	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), Arc::new(Miner::default()), IoChannel::disconnected()).unwrap();
+	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), Arc::new(Miner::with_spec(get_test_spec())), IoChannel::disconnected()).unwrap();
 
     let non_existant = client.block_header(BlockID::Number(188));
 	assert!(non_existant.is_none());
diff --git a/ethcore/src/tests/helpers.rs b/ethcore/src/tests/helpers.rs
index ab538922c..1fefd5830 100644
--- a/ethcore/src/tests/helpers.rs
+++ b/ethcore/src/tests/helpers.rs
@@ -151,7 +151,7 @@ pub fn generate_dummy_client_with_spec_and_data<F>(get_test_spec: F, block_numbe
 	let dir = RandomTempPath::new();
 
 	let test_spec = get_test_spec();
-	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), Arc::new(Miner::default()), IoChannel::disconnected()).unwrap();
+	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), Arc::new(Miner::with_spec(get_test_spec())), IoChannel::disconnected()).unwrap();
 	let test_engine = &test_spec.engine;
 
 	let mut db_result = get_temp_journal_db();
@@ -250,7 +250,7 @@ pub fn push_blocks_to_client(client: &Arc<Client>, timestamp_salt: u64, starting
 
 pub fn get_test_client_with_blocks(blocks: Vec<Bytes>) -> GuardedTempResult<Arc<Client>> {
 	let dir = RandomTempPath::new();
-	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), Arc::new(Miner::default()), IoChannel::disconnected()).unwrap();
+	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), Arc::new(Miner::with_spec(get_test_spec())), IoChannel::disconnected()).unwrap();
 	for block in &blocks {
 		if let Err(_) = client.import_block(block.clone()) {
 			panic!("panic importing block which is well-formed");
diff --git a/parity/main.rs b/parity/main.rs
index cecb0e0a1..62262758d 100644
--- a/parity/main.rs
+++ b/parity/main.rs
@@ -208,8 +208,8 @@ fn execute_client(conf: Configuration, spec: Spec, client_config: ClientConfig)
 	let account_service = Arc::new(conf.account_service());
 
 	// Miner
-	let miner = Miner::with_accounts(conf.args.flag_force_sealing, conf.spec(), account_service.clone());
-	miner.set_author(conf.author().unwrap_or(Default::default()));
+	let miner = Miner::new(conf.args.flag_force_sealing, conf.spec(), Some(account_service.clone()));
+	miner.set_author(conf.author().unwrap_or_default());
 	miner.set_gas_floor_target(conf.gas_floor_target());
 	miner.set_gas_ceil_target(conf.gas_ceil_target());
 	miner.set_extra_data(conf.extra_data());
@@ -341,7 +341,7 @@ fn execute_export(conf: Configuration) {
 
 	// Build client
 	let service = ClientService::start(
-		client_config, spec, net_settings, Path::new(&conf.path()), Arc::new(Miner::default()), false
+		client_config, spec, net_settings, Path::new(&conf.path()), Arc::new(Miner::with_spec(conf.spec())), false
 	).unwrap_or_else(|e| die_with_error("Client", e));
 
 	panic_handler.forward_from(&service);
@@ -413,7 +413,7 @@ fn execute_import(conf: Configuration) {
 
 	// Build client
 	let service = ClientService::start(
-		client_config, spec, net_settings, Path::new(&conf.path()), Arc::new(Miner::default()), false
+		client_config, spec, net_settings, Path::new(&conf.path()), Arc::new(Miner::with_spec(conf.spec())), false
 	).unwrap_or_else(|e| die_with_error("Client", e));
 
 	panic_handler.forward_from(&service);
diff --git a/rpc/src/v1/tests/eth.rs b/rpc/src/v1/tests/eth.rs
index 5cc0176c7..6e2256e24 100644
--- a/rpc/src/v1/tests/eth.rs
+++ b/rpc/src/v1/tests/eth.rs
@@ -49,7 +49,7 @@ fn sync_provider() -> Arc<TestSyncProvider> {
 }
 
 fn miner_service(spec: Spec, accounts: Arc<AccountProvider>) -> Arc<Miner> {
-	Miner::with_accounts(true, spec, accounts)
+	Miner::new(true, spec, Some(accounts))
 }
 
 fn make_spec(chain: &BlockChain) -> Spec {
diff --git a/sync/src/lib.rs b/sync/src/lib.rs
index c3935f5e1..3f899c261 100644
--- a/sync/src/lib.rs
+++ b/sync/src/lib.rs
@@ -44,8 +44,14 @@
 //! 	let mut service = NetworkService::new(NetworkConfiguration::new()).unwrap();
 //! 	service.start().unwrap();
 //! 	let dir = env::temp_dir();
-//! 	let client = Client::new(ClientConfig::default(), ethereum::new_frontier(true), &dir, Arc::new(Miner::default()), service.io().channel()).unwrap();
-//! 	let miner = Miner::new(false, ethereum::new_frontier(true));
+//! 	let miner = Miner::new(false, ethereum::new_frontier(true), None);
+//! 	let client = Client::new(
+//!			ClientConfig::default(),
+//!			ethereum::new_frontier(true),
+//!			&dir,
+//!			miner,
+//!			service.io().channel()
+//!		).unwrap();
 //! 	let sync = EthSync::new(SyncConfig::default(), client);
 //! 	EthSync::register(&mut service, sync);
 //! }