diff --git a/ethcore/src/client/client.rs b/ethcore/src/client/client.rs
index b65bdfd4d..1a437bfac 100644
--- a/ethcore/src/client/client.rs
+++ b/ethcore/src/client/client.rs
@@ -16,7 +16,6 @@
 
 //! Blockchain database client.
 
-use std::marker::PhantomData;
 use std::path::PathBuf;
 use std::sync::atomic::{AtomicUsize, Ordering as AtomicOrdering};
 use util::*;
@@ -30,7 +29,8 @@ use engine::Engine;
 use views::HeaderView;
 use service::{NetSyncMessage, SyncMessage};
 use env_info::LastHashes;
-use verification::*;
+use verification;
+use verification::{PreverifiedBlock, Verifier};
 use block::*;
 use transaction::{LocalizedTransaction, SignedTransaction, Action};
 use blockchain::extras::TransactionAddress;
@@ -83,7 +83,7 @@ impl ClientReport {
 
 /// Blockchain database client backed by a persistent database. Owns and manages a blockchain and a block queue.
 /// Call `import_block()` to import a block asynchronously; `flush_queue()` flushes the queue.
-pub struct Client<V = CanonVerifier> where V: Verifier {
+pub struct Client {
 	chain: Arc<BlockChain>,
 	tracedb: Arc<TraceDB<BlockChain>>,
 	engine: Arc<Box<Engine>>,
@@ -92,7 +92,7 @@ pub struct Client<V = CanonVerifier> where V: Verifier {
 	report: RwLock<ClientReport>,
 	import_lock: Mutex<()>,
 	panic_handler: Arc<PanicHandler>,
-	verifier: PhantomData<V>,
+	verifier: Box<Verifier>,
 	vm_factory: Arc<EvmFactory>,
 	miner: Arc<Miner>,
 	io_channel: IoChannel<NetSyncMessage>,
@@ -107,13 +107,6 @@ const HISTORY: u64 = 1200;
 // of which you actually want force an upgrade.
 const CLIENT_DB_VER_STR: &'static str = "5.3";
 
-impl Client<CanonVerifier> {
-	/// Create a new client with given spec and DB path.
-	pub fn new(config: ClientConfig, spec: Spec, path: &Path, miner: Arc<Miner>, message_channel: IoChannel<NetSyncMessage> ) -> Result<Arc<Client>, ClientError> {
-		Client::<CanonVerifier>::new_with_verifier(config, spec, path, miner, message_channel)
-	}
-}
-
 /// Get the path for the databases given the root path and information on the databases.
 pub fn get_db_path(path: &Path, pruning: journaldb::Algorithm, genesis_hash: H256) -> PathBuf {
 	let mut dir = path.to_path_buf();
@@ -131,15 +124,15 @@ pub fn append_path(path: &Path, item: &str) -> String {
 	p.to_str().unwrap().to_owned()
 }
 
-impl<V> Client<V> where V: Verifier {
+impl Client {
 	///  Create a new client with given spec and DB path and custom verifier.
-	pub fn new_with_verifier(
+	pub fn new(
 		config: ClientConfig,
 		spec: Spec,
 		path: &Path,
 		miner: Arc<Miner>,
 		message_channel: IoChannel<NetSyncMessage>)
-		-> Result<Arc<Client<V>>, ClientError>
+		-> Result<Arc<Client>, ClientError>
 	{
 		let path = get_db_path(path, config.pruning, spec.genesis_header().hash());
 		let gb = spec.genesis_block();
@@ -180,7 +173,7 @@ impl<V> Client<V> where V: Verifier {
 			report: RwLock::new(Default::default()),
 			import_lock: Mutex::new(()),
 			panic_handler: panic_handler,
-			verifier: PhantomData,
+			verifier: verification::new(config.verifier_type),
 			vm_factory: Arc::new(EvmFactory::new(config.vm_type)),
 			miner: miner,
 			io_channel: message_channel,
@@ -222,7 +215,7 @@ impl<V> Client<V> where V: Verifier {
 		}
 
 		// Verify Block Family
-		let verify_family_result = V::verify_block_family(&header, &block.bytes, engine, self.chain.deref());
+		let verify_family_result = self.verifier.verify_block_family(&header, &block.bytes, engine, self.chain.deref());
 		if let Err(e) = verify_family_result {
 			warn!(target: "client", "Stage 3 block verification failed for #{} ({})\nError: {:?}", header.number(), header.hash(), e);
 			return Err(());
@@ -248,7 +241,7 @@ impl<V> Client<V> where V: Verifier {
 
 		// Final Verification
 		let locked_block = enact_result.unwrap();
-		if let Err(e) = V::verify_block_final(&header, locked_block.block().header()) {
+		if let Err(e) = self.verifier.verify_block_final(&header, locked_block.block().header()) {
 			warn!(target: "client", "Stage 4 block verification failed for #{} ({})\nError: {:?}", header.number(), header.hash(), e);
 			return Err(());
 		}
@@ -483,7 +476,7 @@ impl<V> Client<V> where V: Verifier {
 	}
 }
 
-impl<V> BlockChainClient for Client<V> where V: Verifier {
+impl BlockChainClient for Client {
 	fn call(&self, t: &SignedTransaction, analytics: CallAnalytics) -> Result<Executed, ExecutionError> {
 		let header = self.block_header(BlockID::Latest).unwrap();
 		let view = HeaderView::new(&header);
@@ -806,7 +799,7 @@ impl<V> BlockChainClient for Client<V> where V: Verifier {
 	}
 }
 
-impl<V> MiningBlockChainClient for Client<V> where V: Verifier {
+impl MiningBlockChainClient for Client {
 	fn prepare_open_block(&self, author: Address, gas_range_target: (U256, U256), extra_data: Bytes) -> OpenBlock {
 		let engine = self.engine.deref().deref();
 		let h = self.chain.best_block_hash();
diff --git a/ethcore/src/client/config.rs b/ethcore/src/client/config.rs
index 7d7f8e524..52a875a2f 100644
--- a/ethcore/src/client/config.rs
+++ b/ethcore/src/client/config.rs
@@ -18,6 +18,7 @@ pub use block_queue::BlockQueueConfig;
 pub use blockchain::Config as BlockChainConfig;
 pub use trace::{Config as TraceConfig, Switch};
 pub use evm::VMType;
+pub use verification::VerifierType;
 use util::journaldb;
 
 /// Client state db compaction profile
@@ -52,4 +53,6 @@ pub struct ClientConfig {
 	pub db_cache_size: Option<usize>,
 	/// State db compaction profile
 	pub db_compaction: DatabaseCompactionProfile,
+	/// Type of block verifier used by client.
+	pub verifier_type: VerifierType,
 }
diff --git a/ethcore/src/verification/canon_verifier.rs b/ethcore/src/verification/canon_verifier.rs
index 30e368f1b..e0ebf1b7c 100644
--- a/ethcore/src/verification/canon_verifier.rs
+++ b/ethcore/src/verification/canon_verifier.rs
@@ -24,11 +24,11 @@ use super::verification;
 pub struct CanonVerifier;
 
 impl Verifier for CanonVerifier {
-	fn verify_block_family(header: &Header, bytes: &[u8], engine: &Engine, bc: &BlockProvider) -> Result<(), Error> {
+	fn verify_block_family(&self, header: &Header, bytes: &[u8], engine: &Engine, bc: &BlockProvider) -> Result<(), Error> {
 		verification::verify_block_family(header, bytes, engine, bc)
 	}
 
-	fn verify_block_final(expected: &Header, got: &Header) -> Result<(), Error> {
+	fn verify_block_final(&self, expected: &Header, got: &Header) -> Result<(), Error> {
 		verification::verify_block_final(expected, got)
 	}
 }
diff --git a/ethcore/src/verification/mod.rs b/ethcore/src/verification/mod.rs
index fe1f406cc..10aee21f4 100644
--- a/ethcore/src/verification/mod.rs
+++ b/ethcore/src/verification/mod.rs
@@ -17,11 +17,32 @@
 pub mod verification;
 pub mod verifier;
 mod canon_verifier;
-#[cfg(test)]
 mod noop_verifier;
 
 pub use self::verification::*;
 pub use self::verifier::Verifier;
 pub use self::canon_verifier::CanonVerifier;
-#[cfg(test)]
 pub use self::noop_verifier::NoopVerifier;
+
+/// Verifier type.
+#[derive(Debug)]
+pub enum VerifierType {
+	/// Verifies block normally.
+	Canon,
+	/// Does not verify block at all.
+	/// Used in tests.
+	Noop,
+}
+
+impl Default for VerifierType {
+	fn default() -> Self {
+		VerifierType::Canon
+	}
+}
+
+pub fn new(v: VerifierType) -> Box<Verifier> {
+	match v {
+		VerifierType::Canon => Box::new(CanonVerifier),
+		VerifierType::Noop => Box::new(NoopVerifier),
+	}
+}
diff --git a/ethcore/src/verification/noop_verifier.rs b/ethcore/src/verification/noop_verifier.rs
index 20c15c3f1..99d1d594c 100644
--- a/ethcore/src/verification/noop_verifier.rs
+++ b/ethcore/src/verification/noop_verifier.rs
@@ -24,11 +24,11 @@ use super::Verifier;
 pub struct NoopVerifier;
 
 impl Verifier for NoopVerifier {
-	fn verify_block_family(_header: &Header, _bytes: &[u8], _engine: &Engine, _bc: &BlockProvider) -> Result<(), Error> {
+	fn verify_block_family(&self, _header: &Header, _bytes: &[u8], _engine: &Engine, _bc: &BlockProvider) -> Result<(), Error> {
 		Ok(())
 	}
 
-	fn verify_block_final(_expected: &Header, _got: &Header) -> Result<(), Error> {
+	fn verify_block_final(&self, _expected: &Header, _got: &Header) -> Result<(), Error> {
 		Ok(())
 	}
 }
diff --git a/ethcore/src/verification/verifier.rs b/ethcore/src/verification/verifier.rs
index cc5edce29..5db81a4eb 100644
--- a/ethcore/src/verification/verifier.rs
+++ b/ethcore/src/verification/verifier.rs
@@ -21,6 +21,6 @@ use header::Header;
 
 /// Should be used to verify blocks.
 pub trait Verifier: Send + Sync {
-	fn verify_block_family(header: &Header, bytes: &[u8], engine: &Engine, bc: &BlockProvider) -> Result<(), Error>;
-	fn verify_block_final(expected: &Header, got: &Header) -> Result<(), Error>;
+	fn verify_block_family(&self, header: &Header, bytes: &[u8], engine: &Engine, bc: &BlockProvider) -> Result<(), Error>;
+	fn verify_block_final(&self, expected: &Header, got: &Header) -> Result<(), Error>;
 }