diff --git a/ethcore/light/src/client/fetch.rs b/ethcore/light/src/client/fetch.rs
index 2e125bb42..9f4a38dc4 100644
--- a/ethcore/light/src/client/fetch.rs
+++ b/ethcore/light/src/client/fetch.rs
@@ -18,6 +18,7 @@
 
 use std::sync::Arc;
 
+use ethcore::encoded;
 use ethcore::engines::{Engine, StateDependentProof};
 use ethcore::header::Header;
 use ethcore::receipt::Receipt;
@@ -30,7 +31,7 @@ pub trait ChainDataFetcher: Send + Sync + 'static {
 	type Error: ::std::fmt::Debug;
 
 	/// Future for fetching block body.
-	type Body: IntoFuture<Item=Vec<u8>,Error=Self::Error>;
+	type Body: IntoFuture<Item=encoded::Block,Error=Self::Error>;
 	/// Future for fetching block receipts.
 	type Receipts: IntoFuture<Item=Vec<Receipt>,Error=Self::Error>;
 	/// Future for fetching epoch transition
@@ -55,7 +56,7 @@ pub fn unavailable() -> Unavailable { Unavailable }
 impl ChainDataFetcher for Unavailable {
 	type Error = &'static str;
 
-	type Body = Result<Vec<u8>, &'static str>;
+	type Body = Result<encoded::Block, &'static str>;
 	type Receipts = Result<Vec<Receipt>, &'static str>;
 	type Transition = Result<Vec<u8>, &'static str>;
 
diff --git a/ethcore/light/src/client/mod.rs b/ethcore/light/src/client/mod.rs
index 9c8e1da50..569acecc6 100644
--- a/ethcore/light/src/client/mod.rs
+++ b/ethcore/light/src/client/mod.rs
@@ -83,6 +83,9 @@ impl Default for Config {
 
 /// Trait for interacting with the header chain abstractly.
 pub trait LightChainClient: Send + Sync {
+	/// Adds a new `LightChainNotify` listener.
+	fn add_listener(&self, listener: Weak<LightChainNotify>);
+
 	/// Get chain info.
 	fn chain_info(&self) -> BlockChainInfo;
 
@@ -481,7 +484,7 @@ impl<T: ChainDataFetcher> Client<T> {
 				};
 
 				if let Some(b) = b {
-					block = Some(b.into_future().wait()?);
+					block = Some(b.into_future().wait()?.into_inner());
 				}
 
 				if let Some(r) = r {
@@ -526,6 +529,10 @@ impl<T: ChainDataFetcher> Client<T> {
 }
 
 impl<T: ChainDataFetcher> LightChainClient for Client<T> {
+	fn add_listener(&self, listener: Weak<LightChainNotify>) {
+		Client::add_listener(self, listener)
+	}
+
 	fn chain_info(&self) -> BlockChainInfo { Client::chain_info(self) }
 
 	fn queue_header(&self, header: Header) -> Result<H256, BlockImportError> {
diff --git a/ethcore/src/header.rs b/ethcore/src/header.rs
index a9a4f948d..a256b5c87 100644
--- a/ethcore/src/header.rs
+++ b/ethcore/src/header.rs
@@ -259,6 +259,11 @@ impl Header {
 
 	/// Get the SHA3 (Keccak) of this header, optionally `with_seal`.
 	pub fn rlp_sha3(&self, with_seal: Seal) -> H256 { self.rlp(with_seal).sha3() }
+
+	/// Encode the header, getting a type-safe wrapper around the RLP.
+	pub fn encoded(&self) -> ::encoded::Header {
+		::encoded::Header::new(self.rlp(Seal::With))
+	}
 }
 
 impl Decodable for Header {
diff --git a/parity/blockchain.rs b/parity/blockchain.rs
index 426c8d447..d9821c5bb 100644
--- a/parity/blockchain.rs
+++ b/parity/blockchain.rs
@@ -204,7 +204,9 @@ fn execute_import_light(cmd: ImportBlockchain) -> Result<(), String> {
 	config.queue.max_mem_use = cmd.cache_config.queue() as usize * 1024 * 1024;
 	config.queue.verifier_settings = cmd.verifier_settings;
 
-	let service = LightClientService::start(config, &spec, &client_path, cache)
+	// TODO: could epoch signals be avilable at the end of the file?
+	let fetch = ::light::client::fetch::unavailable();
+	let service = LightClientService::start(config, &spec, fetch, &client_path, cache)
 		.map_err(|e| format!("Failed to start client: {}", e))?;
 
 	// free up the spec in memory.
diff --git a/parity/dapps.rs b/parity/dapps.rs
index fddd050f5..b7ca739ec 100644
--- a/parity/dapps.rs
+++ b/parity/dapps.rs
@@ -26,7 +26,7 @@ use futures_cpupool::CpuPool;
 use hash_fetch::fetch::Client as FetchClient;
 use hash_fetch::urlhint::ContractClient;
 use helpers::replace_home;
-use light::client::Client as LightClient;
+use light::client::LightChainClient;
 use light::on_demand::{self, OnDemand};
 use rpc;
 use rpc_apis::SignerService;
@@ -94,16 +94,16 @@ impl ContractClient for FullRegistrar {
 }
 
 /// Registrar implementation for the light client.
-pub struct LightRegistrar {
+pub struct LightRegistrar<T> {
 	/// The light client.
-	pub client: Arc<LightClient>,
+	pub client: Arc<T>,
 	/// Handle to the on-demand service.
 	pub on_demand: Arc<OnDemand>,
 	/// Handle to the light network service.
 	pub sync: Arc<LightSync>,
 }
 
-impl ContractClient for LightRegistrar {
+impl<T: LightChainClient + 'static> ContractClient for LightRegistrar<T> {
 	fn registrar(&self) -> Result<Address, String> {
 		self.client.engine().additional_params().get("registrar")
 			 .ok_or_else(|| "Registrar not defined.".into())
@@ -113,7 +113,14 @@ impl ContractClient for LightRegistrar {
 	}
 
 	fn call(&self, address: Address, data: Bytes) -> BoxFuture<Bytes, String> {
-		let (header, env_info) = (self.client.best_block_header(), self.client.latest_env_info());
+		let header = self.client.best_block_header();
+		let env_info = self.client.env_info(BlockId::Hash(header.hash()))
+			.ok_or_else(|| format!("Cannot fetch env info for header {}", header.hash()));
+
+		let env_info = match env_info {
+			Ok(x) => x,
+			Err(e) => return future::err(e).boxed(),
+		};
 
 		let maybe_future = self.sync.with_context(move |ctx| {
 			self.on_demand
diff --git a/parity/informant.rs b/parity/informant.rs
index 1935ec9b6..2be83d566 100644
--- a/parity/informant.rs
+++ b/parity/informant.rs
@@ -22,7 +22,7 @@ use std::sync::{Arc};
 use std::sync::atomic::{AtomicUsize, AtomicBool, Ordering as AtomicOrdering};
 use std::time::{Instant, Duration};
 
-use ethcore::client::*;
+use ethcore::client::{BlockId, BlockChainClient, BlockChainInfo, BlockQueueInfo, ChainNotify, ClientReport, Client};
 use ethcore::header::BlockNumber;
 use ethcore::service::ClientIoMessage;
 use ethcore::snapshot::{RestorationStatus, SnapshotService as SS};
diff --git a/parity/light_helpers/epoch_fetch.rs b/parity/light_helpers/epoch_fetch.rs
new file mode 100644
index 000000000..d710abb9f
--- /dev/null
+++ b/parity/light_helpers/epoch_fetch.rs
@@ -0,0 +1,89 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use std::sync::{Arc, Weak};
+
+use ethcore::encoded;
+use ethcore::engines::{Engine, StateDependentProof};
+use ethcore::header::Header;
+use ethcore::receipt::Receipt;
+use ethsync::LightSync;
+
+use futures::{future, Future, BoxFuture};
+
+use light::client::fetch::ChainDataFetcher;
+use light::on_demand::{request, OnDemand};
+
+use util::{RwLock, H256};
+
+const ALL_VALID_BACKREFS: &str = "no back-references, therefore all back-references valid; qed";
+
+/// Allows on-demand fetch of data useful for the light client.
+pub struct EpochFetch {
+	/// A handle to the sync service.
+	pub sync: Arc<RwLock<Weak<LightSync>>>,
+	/// The on-demand request service.
+	pub on_demand: Arc<OnDemand>,
+}
+
+impl EpochFetch {
+	fn request<T>(&self, req: T) -> BoxFuture<T::Out, &'static str>
+		where T: Send + request::RequestAdapter + 'static, T::Out: Send + 'static
+	{
+		match self.sync.read().upgrade() {
+			Some(sync) => {
+				let on_demand = &self.on_demand;
+				let maybe_future = sync.with_context(move |ctx| {
+					on_demand.request(ctx, req).expect(ALL_VALID_BACKREFS)
+				});
+
+				match maybe_future {
+					Some(x) => x.map_err(|_| "Request canceled").boxed(),
+					None => future::err("Unable to access network.").boxed(),
+				}
+			}
+			None => future::err("Unable to access network").boxed(),
+		}
+	}
+}
+
+impl ChainDataFetcher for EpochFetch {
+	type Error = &'static str;
+
+	type Body = BoxFuture<encoded::Block, &'static str>;
+	type Receipts = BoxFuture<Vec<Receipt>, &'static str>;
+	type Transition = BoxFuture<Vec<u8>, &'static str>;
+
+	fn block_body(&self, header: &Header) -> Self::Body {
+		self.request(request::Body(header.encoded().into()))
+	}
+
+	/// Fetch block receipts.
+	fn block_receipts(&self, header: &Header) -> Self::Receipts {
+		self.request(request::BlockReceipts(header.encoded().into()))
+	}
+
+	/// Fetch epoch transition proof at given header.
+	fn epoch_transition(&self, hash: H256, engine: Arc<Engine>, checker: Arc<StateDependentProof>)
+		-> Self::Transition
+	{
+		self.request(request::Signal {
+			hash: hash,
+			engine: engine,
+			proof_check: checker,
+		})
+	}
+}
diff --git a/parity/light_helpers/mod.rs b/parity/light_helpers/mod.rs
index 488f970c2..5fc9c516b 100644
--- a/parity/light_helpers/mod.rs
+++ b/parity/light_helpers/mod.rs
@@ -16,6 +16,8 @@
 
 //! Utilities and helpers for the light client.
 
+mod epoch_fetch;
 mod queue_cull;
 
+pub use self::epoch_fetch::EpochFetch;
 pub use self::queue_cull::QueueCull;
diff --git a/parity/light_helpers/queue_cull.rs b/parity/light_helpers/queue_cull.rs
index 982e69e48..34769b864 100644
--- a/parity/light_helpers/queue_cull.rs
+++ b/parity/light_helpers/queue_cull.rs
@@ -23,7 +23,7 @@ use ethcore::service::ClientIoMessage;
 use ethsync::LightSync;
 use io::{IoContext, IoHandler, TimerToken};
 
-use light::client::Client;
+use light::client::LightChainClient;
 use light::on_demand::{request, OnDemand};
 use light::TransactionQueue;
 
@@ -41,9 +41,9 @@ const TIMEOUT_MS: u64 = 1000 * 60 * 10;
 const PURGE_TIMEOUT_MS: u64 = 1000 * 60 * 9;
 
 /// Periodically culls the transaction queue of mined transactions.
-pub struct QueueCull {
+pub struct QueueCull<T> {
 	/// A handle to the client, for getting the latest block header.
-	pub client: Arc<Client>,
+	pub client: Arc<T>,
 	/// A handle to the sync service.
 	pub sync: Arc<LightSync>,
 	/// The on-demand request service.
@@ -54,7 +54,7 @@ pub struct QueueCull {
 	pub remote: Remote,
 }
 
-impl IoHandler<ClientIoMessage> for QueueCull {
+impl<T: LightChainClient + 'static> IoHandler<ClientIoMessage> for QueueCull<T> {
 	fn initialize(&self, io: &IoContext<ClientIoMessage>) {
 		io.register_timer(TOKEN, TIMEOUT_MS).expect("Error registering timer");
 	}
diff --git a/parity/rpc_apis.rs b/parity/rpc_apis.rs
index dba69ae7e..bb1e1c377 100644
--- a/parity/rpc_apis.rs
+++ b/parity/rpc_apis.rs
@@ -34,6 +34,7 @@ use ethsync::{ManageNetwork, SyncProvider, LightSync};
 use hash_fetch::fetch::Client as FetchClient;
 use jsonrpc_core::{self as core, MetaIoHandler};
 use light::{TransactionQueue as LightTransactionQueue, Cache as LightDataCache};
+use light::client::LightChainClient;
 use updater::Updater;
 use util::{Mutex, RwLock};
 use ethcore_logger::RotatingLogger;
@@ -395,9 +396,9 @@ impl ActivityNotifier for LightClientNotifier {
 }
 
 /// RPC dependencies for a light client.
-pub struct LightDependencies {
+pub struct LightDependencies<T> {
 	pub signer_service: Arc<SignerService>,
-	pub client: Arc<::light::client::Client>,
+	pub client: Arc<T>,
 	pub sync: Arc<LightSync>,
 	pub net: Arc<ManageNetwork>,
 	pub secret_store: Arc<AccountProvider>,
@@ -415,7 +416,7 @@ pub struct LightDependencies {
 	pub whisper_rpc: Option<::whisper::RpcFactory>,
 }
 
-impl LightDependencies {
+impl<C: LightChainClient + 'static> LightDependencies<C> {
 	fn extend_api<T: core::Middleware<Metadata>>(
 		&self,
 		handler: &mut MetaIoHandler<Metadata, T>,
@@ -563,7 +564,7 @@ impl LightDependencies {
 	}
 }
 
-impl Dependencies for LightDependencies {
+impl<T: LightChainClient + 'static> Dependencies for LightDependencies<T> {
 	type Notifier = LightClientNotifier;
 
 	fn activity_notifier(&self) -> Self::Notifier { LightClientNotifier }
diff --git a/parity/run.rs b/parity/run.rs
index 49624480c..277ee9025 100644
--- a/parity/run.rs
+++ b/parity/run.rs
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
-use std::sync::Arc;
+use std::sync::{Arc, Weak};
 use std::net::{TcpListener};
 
 use ctrlc::CtrlC;
@@ -217,7 +217,16 @@ fn execute_light(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) ->
 	config.queue.max_mem_use = cmd.cache_config.queue() as usize * 1024 * 1024;
 	config.queue.verifier_settings = cmd.verifier_settings;
 
-	let service = light_client::Service::start(config, &spec, &db_dirs.client_path(algorithm), cache.clone())
+	// start on_demand service.
+	let on_demand = Arc::new(::light::on_demand::OnDemand::new(cache.clone()));
+
+	let sync_handle = Arc::new(RwLock::new(Weak::new()));
+	let fetch = ::light_helpers::EpochFetch {
+		on_demand: on_demand.clone(),
+		sync: sync_handle.clone(),
+	};
+
+	let service = light_client::Service::start(config, &spec, fetch, &db_dirs.client_path(algorithm), cache.clone())
 		.map_err(|e| format!("Error starting light client: {}", e))?;
 	let txq = Arc::new(RwLock::new(::light::transaction_queue::TransactionQueue::default()));
 	let provider = ::light::provider::LightProvider::new(service.client().clone(), txq.clone());
@@ -229,9 +238,6 @@ fn execute_light(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) ->
 		net_conf.boot_nodes = spec.nodes.clone();
 	}
 
-	// start on_demand service.
-	let on_demand = Arc::new(::light::on_demand::OnDemand::new(cache.clone()));
-
 	let mut attached_protos = Vec::new();
 	let whisper_factory = if cmd.whisper.enabled {
 		let (whisper_net, whisper_factory) = ::whisper::setup(cmd.whisper.target_message_pool_size)
@@ -255,6 +261,7 @@ fn execute_light(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) ->
 	};
 	let light_sync = LightSync::new(sync_params).map_err(|e| format!("Error starting network: {}", e))?;
 	let light_sync = Arc::new(light_sync);
+	*sync_handle.write() = Arc::downgrade(&light_sync);
 
 	// spin up event loop
 	let event_loop = EventLoop::spawn();
diff --git a/rpc/src/v1/impls/light/eth.rs b/rpc/src/v1/impls/light/eth.rs
index d33b5a06f..b515d7961 100644
--- a/rpc/src/v1/impls/light/eth.rs
+++ b/rpc/src/v1/impls/light/eth.rs
@@ -25,7 +25,7 @@ use jsonrpc_core::Error;
 use jsonrpc_macros::Trailing;
 
 use light::cache::Cache as LightDataCache;
-use light::client::{Client as LightClient, LightChainClient};
+use light::client::LightChainClient;
 use light::{cht, TransactionQueue};
 use light::on_demand::{request, OnDemand};
 
@@ -62,9 +62,9 @@ use util::Address;
 const NO_INVALID_BACK_REFS: &'static str = "Fails only on invalid back-references; back-references here known to be valid; qed";
 
 /// Light client `ETH` (and filter) RPC.
-pub struct EthClient {
+pub struct EthClient<T> {
 	sync: Arc<LightSync>,
-	client: Arc<LightClient>,
+	client: Arc<T>,
 	on_demand: Arc<OnDemand>,
 	transaction_queue: Arc<RwLock<TransactionQueue>>,
 	accounts: Arc<AccountProvider>,
@@ -72,7 +72,7 @@ pub struct EthClient {
 	polls: Mutex<PollManager<PollFilter>>,
 }
 
-impl Clone for EthClient {
+impl<T> Clone for EthClient<T> {
 	fn clone(&self) -> Self {
 		// each instance should have its own poll manager.
 		EthClient {
@@ -88,12 +88,12 @@ impl Clone for EthClient {
 }
 
 
-impl EthClient {
+impl<T: LightChainClient + 'static> EthClient<T> {
 	/// Create a new `EthClient` with a handle to the light sync instance, client,
 	/// and on-demand request service, which is assumed to be attached as a handler.
 	pub fn new(
 		sync: Arc<LightSync>,
-		client: Arc<LightClient>,
+		client: Arc<T>,
 		on_demand: Arc<OnDemand>,
 		transaction_queue: Arc<RwLock<TransactionQueue>>,
 		accounts: Arc<AccountProvider>,
@@ -208,7 +208,7 @@ impl EthClient {
 	}
 }
 
-impl Eth for EthClient {
+impl<T: LightChainClient + 'static> Eth for EthClient<T> {
 	type Metadata = Metadata;
 
 	fn protocol_version(&self) -> Result<String, Error> {
@@ -465,7 +465,7 @@ impl Eth for EthClient {
 }
 
 // This trait implementation triggers a blanked impl of `EthFilter`.
-impl Filterable for EthClient {
+impl<T: LightChainClient + 'static> Filterable for EthClient<T> {
 	fn best_block_number(&self) -> u64 { self.client.chain_info().best_block_number }
 
 	fn block_hash(&self, id: BlockId) -> Option<RpcH256> {
diff --git a/sync/src/chain.rs b/sync/src/chain.rs
index 3a472c88f..a4708a12d 100644
--- a/sync/src/chain.rs
+++ b/sync/src/chain.rs
@@ -2238,7 +2238,7 @@ mod tests {
 	use super::{PeerInfo, PeerAsking};
 	use ethkey;
 	use ethcore::header::*;
-	use ethcore::client::*;
+	use ethcore::client::{BlockChainClient, EachBlockWith, TestBlockChainClient};
 	use ethcore::transaction::UnverifiedTransaction;
 	use ethcore::miner::MinerService;
 
diff --git a/sync/src/light_sync/tests/test_net.rs b/sync/src/light_sync/tests/test_net.rs
index f6d5eddf0..51cb796de 100644
--- a/sync/src/light_sync/tests/test_net.rs
+++ b/sync/src/light_sync/tests/test_net.rs
@@ -25,7 +25,7 @@ use tests::helpers::{TestNet, Peer as PeerLike, TestPacket};
 use ethcore::client::TestBlockChainClient;
 use ethcore::spec::Spec;
 use io::IoChannel;
-use light::client::Client as LightClient;
+use light::client::fetch::{self, Unavailable};
 use light::net::{LightProtocol, IoContext, Capabilities, Params as LightParams};
 use light::provider::LightProvider;
 use network::{NodeId, PeerId};
@@ -36,6 +36,8 @@ use light::cache::Cache;
 
 const NETWORK_ID: u64 = 0xcafebabe;
 
+pub type LightClient = ::light::client::Client<Unavailable>;
+
 struct TestIoContext<'a> {
 	queue: &'a RwLock<VecDeque<TestPacket>>,
 	sender: Option<PeerId>,
@@ -216,7 +218,14 @@ impl TestNet<Peer> {
 			// skip full verification because the blocks are bad.
 			config.verify_full = false;
 			let cache = Arc::new(Mutex::new(Cache::new(Default::default(), Duration::hours(6))));
-			let client = LightClient::in_memory(config, &Spec::new_test(), IoChannel::disconnected(), cache);
+			let client = LightClient::in_memory(
+				config,
+				&Spec::new_test(),
+				fetch::unavailable(), // TODO: allow fetch from full nodes.
+				IoChannel::disconnected(),
+				cache
+			);
+
 			peers.push(Arc::new(Peer::new_light(Arc::new(client))))
 		}
 
diff --git a/sync/src/tests/consensus.rs b/sync/src/tests/consensus.rs
index 9b01156b7..c31ea692f 100644
--- a/sync/src/tests/consensus.rs
+++ b/sync/src/tests/consensus.rs
@@ -69,8 +69,8 @@ fn authority_round() {
 	// Push transaction to both clients. Only one of them gets lucky to produce a block.
 	net.peer(0).chain.miner().set_engine_signer(s0.address(), "".to_owned()).unwrap();
 	net.peer(1).chain.miner().set_engine_signer(s1.address(), "".to_owned()).unwrap();
-	net.peer(0).chain.engine().register_client(Arc::downgrade(&net.peer(0).chain));
-	net.peer(1).chain.engine().register_client(Arc::downgrade(&net.peer(1).chain));
+	net.peer(0).chain.engine().register_client(Arc::downgrade(&net.peer(0).chain) as _);
+	net.peer(1).chain.engine().register_client(Arc::downgrade(&net.peer(1).chain) as _);
 	net.peer(0).chain.set_io_channel(IoChannel::to_handler(Arc::downgrade(&io_handler1)));
 	net.peer(1).chain.set_io_channel(IoChannel::to_handler(Arc::downgrade(&io_handler0)));
 	// exchange statuses
@@ -158,8 +158,8 @@ fn tendermint() {
 	trace!(target: "poa", "Peer 0 is {}.", s0.address());
 	net.peer(1).chain.miner().set_engine_signer(s1.address(), "".to_owned()).unwrap();
 	trace!(target: "poa", "Peer 1 is {}.", s1.address());
-	net.peer(0).chain.engine().register_client(Arc::downgrade(&net.peer(0).chain));
-	net.peer(1).chain.engine().register_client(Arc::downgrade(&net.peer(1).chain));
+	net.peer(0).chain.engine().register_client(Arc::downgrade(&net.peer(0).chain) as _);
+	net.peer(1).chain.engine().register_client(Arc::downgrade(&net.peer(1).chain) as _);
 	net.peer(0).chain.set_io_channel(IoChannel::to_handler(Arc::downgrade(&io_handler0)));
 	net.peer(1).chain.set_io_channel(IoChannel::to_handler(Arc::downgrade(&io_handler1)));
 	// Exhange statuses