diff --git a/ethcore/src/client/client.rs b/ethcore/src/client/client.rs
index 0d61325d9..041dfd92a 100644
--- a/ethcore/src/client/client.rs
+++ b/ethcore/src/client/client.rs
@@ -21,7 +21,7 @@ use std::path::PathBuf;
 use util::*;
 use util::panics::*;
 use views::BlockView;
-use error::*;
+use error::{Error, ImportError, ExecutionError, BlockError, ImportResult};
 use header::{BlockNumber, Header};
 use state::State;
 use spec::Spec;
@@ -38,6 +38,7 @@ use log_entry::LocalizedLogEntry;
 use block_queue::{BlockQueue, BlockQueueInfo};
 use blockchain::{BlockChain, BlockProvider, TreeRoute, ImportRoute};
 use client::{BlockId, TransactionId, UncleId, TraceId, ClientConfig, BlockChainClient, TraceFilter};
+use client::Error as ClientError;
 use env_info::EnvInfo;
 use executive::{Executive, Executed, TransactOptions, contract_address};
 use receipt::LocalizedReceipt;
@@ -99,7 +100,7 @@ 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, message_channel: IoChannel<NetSyncMessage> ) -> Arc<Client> {
+	pub fn new(config: ClientConfig, spec: Spec, path: &Path, message_channel: IoChannel<NetSyncMessage> ) -> Result<Arc<Client>, ClientError> {
 		Client::<CanonVerifier>::new_with_verifier(config, spec, path, message_channel)
 	}
 }
@@ -123,11 +124,11 @@ pub fn append_path(path: &Path, item: &str) -> String {
 
 impl<V> Client<V> where V: Verifier {
 	///  Create a new client with given spec and DB path and custom verifier.
-	pub fn new_with_verifier(config: ClientConfig, spec: Spec, path: &Path, message_channel: IoChannel<NetSyncMessage> ) -> Arc<Client<V>> {
+	pub fn new_with_verifier(config: ClientConfig, spec: Spec, path: &Path, message_channel: IoChannel<NetSyncMessage> ) -> Result<Arc<Client<V>>, ClientError> {
 		let path = get_db_path(path, config.pruning, spec.genesis_header().hash());
 		let gb = spec.genesis_block();
 		let chain = Arc::new(BlockChain::new(config.blockchain, &gb, &path));
-		let tracedb = Arc::new(TraceDB::new(config.tracing, &path, chain.clone()));
+		let tracedb = Arc::new(try!(TraceDB::new(config.tracing, &path, chain.clone())));
 
 		let mut state_db = journaldb::new(&append_path(&path, "state"), config.pruning);
 
@@ -141,7 +142,7 @@ impl<V> Client<V> where V: Verifier {
 		let panic_handler = PanicHandler::new_in_arc();
 		panic_handler.forward_from(&block_queue);
 
-		Arc::new(Client {
+		let client = Client {
 			chain: chain,
 			tracedb: tracedb,
 			engine: engine,
@@ -151,7 +152,9 @@ impl<V> Client<V> where V: Verifier {
 			import_lock: Mutex::new(()),
 			panic_handler: panic_handler,
 			verifier: PhantomData,
-		})
+		};
+
+		Ok(Arc::new(client))
 	}
 
 	/// Flush the block import queue.
diff --git a/ethcore/src/client/error.rs b/ethcore/src/client/error.rs
new file mode 100644
index 000000000..fde22cb10
--- /dev/null
+++ b/ethcore/src/client/error.rs
@@ -0,0 +1,23 @@
+use trace::Error as TraceError;
+use std::fmt::{Display, Formatter, Error as FmtError};
+
+/// Client configuration errors.
+#[derive(Debug)]
+pub enum Error {
+	/// TraceDB configuration error.
+	Trace(TraceError),
+}
+
+impl From<TraceError> for Error {
+	fn from(err: TraceError) -> Self {
+		Error::Trace(err)
+	}
+}
+
+impl Display for Error {
+	fn fmt(&self, f: &mut Formatter) -> Result<(), FmtError> {
+		match *self {
+			Error::Trace(ref err) => write!(f, "{}", err)
+		}
+	}
+}
diff --git a/ethcore/src/client/mod.rs b/ethcore/src/client/mod.rs
index a748ff900..28237a3c1 100644
--- a/ethcore/src/client/mod.rs
+++ b/ethcore/src/client/mod.rs
@@ -18,11 +18,13 @@
 
 mod client;
 mod config;
+mod error;
 mod test_client;
 mod trace;
 
 pub use self::client::*;
 pub use self::config::{ClientConfig, BlockQueueConfig, BlockChainConfig, Switch};
+pub use self::error::Error;
 pub use types::ids::*;
 pub use self::test_client::{TestBlockChainClient, EachBlockWith};
 pub use self::trace::Filter as TraceFilter;
diff --git a/ethcore/src/error.rs b/ethcore/src/error.rs
index edec7c959..110d37a0b 100644
--- a/ethcore/src/error.rs
+++ b/ethcore/src/error.rs
@@ -19,6 +19,7 @@
 use util::*;
 use header::BlockNumber;
 use basic_types::LogBloom;
+use client::Error as ClientError;
 
 pub use types::executed::ExecutionError;
 
@@ -134,6 +135,8 @@ pub enum ImportError {
 #[derive(Debug)]
 /// General error type which should be capable of representing all errors in ethcore.
 pub enum Error {
+	/// Client configuration error.
+	Client(ClientError),
 	/// Error concerning a utility.
 	Util(UtilError),
 	/// Error concerning block processing.
@@ -155,6 +158,12 @@ pub enum Error {
 /// Result of import block operation.
 pub type ImportResult = Result<H256, Error>;
 
+impl From<ClientError> for Error {
+	fn from(err: ClientError) -> Error {
+		Error::Client(err)
+	}
+}
+
 impl From<TransactionError> for Error {
 	fn from(err: TransactionError) -> Error {
 		Error::Transaction(err)
diff --git a/ethcore/src/service.rs b/ethcore/src/service.rs
index 2464b7cc6..38bd873b8 100644
--- a/ethcore/src/service.rs
+++ b/ethcore/src/service.rs
@@ -61,7 +61,7 @@ impl ClientService {
 
 		info!("Starting {}", net_service.host_info());
 		info!("Configured for {} using {:?} engine", spec.name, spec.engine.name());
-		let client = Client::new(config, spec, db_path, net_service.io().channel());
+		let client = try!(Client::new(config, spec, db_path, net_service.io().channel()));
 		panic_handler.forward_from(client.deref());
 		let client_io = Arc::new(ClientIoHandler {
 			client: client.clone()
diff --git a/ethcore/src/tests/client.rs b/ethcore/src/tests/client.rs
index 926009ac4..25531692b 100644
--- a/ethcore/src/tests/client.rs
+++ b/ethcore/src/tests/client.rs
@@ -23,7 +23,7 @@ use devtools::*;
 #[test]
 fn imports_from_empty() {
 	let dir = RandomTempPath::new();
-	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), IoChannel::disconnected());
+	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), IoChannel::disconnected()).unwrap();
 	client.import_verified_blocks(&IoChannel::disconnected());
 	client.flush_queue();
 }
@@ -41,7 +41,7 @@ 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(), IoChannel::disconnected());
+	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), 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");
@@ -56,7 +56,7 @@ 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(), IoChannel::disconnected());
+	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), 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 56e33d76b..152ac0ef6 100644
--- a/ethcore/src/tests/helpers.rs
+++ b/ethcore/src/tests/helpers.rs
@@ -145,7 +145,7 @@ pub fn create_test_block_with_data(header: &Header, transactions: &[&SignedTrans
 pub fn generate_dummy_client(block_number: u32) -> GuardedTempResult<Arc<Client>> {
 	let dir = RandomTempPath::new();
 
-	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), IoChannel::disconnected());
+	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), IoChannel::disconnected()).unwrap();
 	let test_spec = get_test_spec();
 	let test_engine = &test_spec.engine;
 	let state_root = test_spec.genesis_header().state_root;
@@ -211,7 +211,7 @@ 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(), IoChannel::disconnected());
+	let client = Client::new(ClientConfig::default(), get_test_spec(), dir.as_path(), 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/ethcore/src/trace/config.rs b/ethcore/src/trace/config.rs
index 3390fb2aa..76c62b43d 100644
--- a/ethcore/src/trace/config.rs
+++ b/ethcore/src/trace/config.rs
@@ -16,6 +16,7 @@
 
 //! Traces config.
 use bloomchain::Config as BloomConfig;
+use trace::Error;
 
 /// 3-value enum.
 #[derive(Debug, Clone, Copy, PartialEq)]
@@ -30,10 +31,10 @@ pub enum Switch {
 
 impl Switch {
 	/// Tries to turn old switch to new value.
-	pub fn turn_to(&self, to: Switch) -> Result<bool, &'static str> {
+	pub fn turn_to(&self, to: Switch) -> Result<bool, Error> {
 		match (*self, to) {
 			(Switch::On, Switch::On) | (Switch::On, Switch::Auto) | (Switch::Auto, Switch::On) => Ok(true),
-			(Switch::Off, Switch::On) => Err("Tracing can't be enabled"),
+			(Switch::Off, Switch::On) => Err(Error::ResyncRequired),
 			_ => Ok(false),
 		}
 	}
diff --git a/ethcore/src/trace/db.rs b/ethcore/src/trace/db.rs
index 5c88ee52b..bf78ef7c5 100644
--- a/ethcore/src/trace/db.rs
+++ b/ethcore/src/trace/db.rs
@@ -25,7 +25,7 @@ use bloomchain::group::{BloomGroupDatabase, BloomGroupChain, GroupPosition, Bloo
 use util::{FixedHash, H256, H264, Database, DBTransaction};
 use header::BlockNumber;
 use trace::{BlockTraces, LocalizedTrace, Config, Switch, Filter, Database as TraceDatabase, ImportRequest,
-DatabaseExtras};
+DatabaseExtras, Error};
 use db::{Key, Writable, Readable, CacheUpdatePolicy};
 use super::bloom::{TraceGroupPosition, BlockTracesBloom, BlockTracesBloomGroup};
 use super::flat::{FlatTrace, FlatBlockTraces, FlatTransactionTraces};
@@ -103,7 +103,7 @@ impl<T> BloomGroupDatabase for TraceDB<T> where T: DatabaseExtras {
 
 impl<T> TraceDB<T> where T: DatabaseExtras {
 	/// Creates new instance of `TraceDB`.
-	pub fn new(config: Config, path: &Path, extras: Arc<T>) -> Self {
+	pub fn new(config: Config, path: &Path, extras: Arc<T>) -> Result<Self, Error> {
 		let mut tracedb_path = path.to_path_buf();
 		tracedb_path.push("tracedb");
 		let tracesdb = Database::open_default(tracedb_path.to_str().unwrap()).unwrap();
@@ -116,7 +116,7 @@ impl<T> TraceDB<T> where T: DatabaseExtras {
 			None => Switch::Auto,
 		};
 
-		let enabled = old_tracing.turn_to(config.enabled).expect("Tracing can't be enabled. Resync required.");
+		let enabled = try!(old_tracing.turn_to(config.enabled));
 
 		let encoded_tracing = match enabled {
 			true => [0x1],
@@ -126,14 +126,16 @@ impl<T> TraceDB<T> where T: DatabaseExtras {
 		tracesdb.put(b"enabled", &encoded_tracing).unwrap();
 		tracesdb.put(b"version", TRACE_DB_VER).unwrap();
 
-		TraceDB {
+		let db = TraceDB {
 			traces: RwLock::new(HashMap::new()),
 			blooms: RwLock::new(HashMap::new()),
 			tracesdb: tracesdb,
 			bloom_config: config.blooms,
 			enabled: enabled,
 			extras: extras,
-		}
+		};
+
+		Ok(db)
 	}
 
 	/// Returns traces for block with hash.
@@ -401,19 +403,19 @@ mod tests {
 		config.enabled = Switch::Auto;
 
 		{
-			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras));
+			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras)).unwrap();
 			assert_eq!(tracedb.tracing_enabled(), false);
 		}
 
 		{
-			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras));
+			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras)).unwrap();
 			assert_eq!(tracedb.tracing_enabled(), false);
 		}
 
 		config.enabled = Switch::Off;
 
 		{
-			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras));
+			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras)).unwrap();
 			assert_eq!(tracedb.tracing_enabled(), false);
 		}
 	}
@@ -427,26 +429,26 @@ mod tests {
 		config.enabled = Switch::On;
 
 		{
-			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras));
+			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras)).unwrap();
 			assert_eq!(tracedb.tracing_enabled(), true);
 		}
 
 		{
-			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras));
+			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras)).unwrap();
 			assert_eq!(tracedb.tracing_enabled(), true);
 		}
 
 		config.enabled = Switch::Auto;
 
 		{
-			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras));
+			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras)).unwrap();
 			assert_eq!(tracedb.tracing_enabled(), true);
 		}
 
 		config.enabled = Switch::Off;
 
 		{
-			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras));
+			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras)).unwrap();
 			assert_eq!(tracedb.tracing_enabled(), false);
 		}
 	}
@@ -461,12 +463,12 @@ mod tests {
 		config.enabled = Switch::Off;
 
 		{
-			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras));
+			let tracedb = TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras)).unwrap();
 			assert_eq!(tracedb.tracing_enabled(), true);
 		}
 
 		config.enabled = Switch::On;
-		TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras)); // should panic!
+		TraceDB::new(config.clone(), temp.as_path(), Arc::new(NoopExtras)).unwrap(); // should panic!
 	}
 
 	fn create_simple_import_request(block_number: BlockNumber, block_hash: H256) -> ImportRequest {
@@ -526,7 +528,7 @@ mod tests {
 		extras.transaction_hashes.insert(0, vec![tx_0.clone()]);
 		extras.transaction_hashes.insert(1, vec![tx_1.clone()]);
 
-		let tracedb = TraceDB::new(config, temp.as_path(), Arc::new(extras));
+		let tracedb = TraceDB::new(config, temp.as_path(), Arc::new(extras)).unwrap();
 
 		// import block 0
 		let request = create_simple_import_request(0, block_0.clone());
diff --git a/ethcore/src/trace/error.rs b/ethcore/src/trace/error.rs
new file mode 100644
index 000000000..0f3cbc62c
--- /dev/null
+++ b/ethcore/src/trace/error.rs
@@ -0,0 +1,48 @@
+// Copyright 2015, 2016 Ethcore (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/>.
+
+//! TraceDB errors.
+
+use std::fmt::{Debug, Display, Formatter, Error as FmtError};
+
+const RESYNC_ERR: &'static str =
+"Your current parity installation has synced without transaction tracing. To use
+Parity with transaction tracing, you'll need to resync with tracing. To do this, remove or move away your current
+database and restart parity. e.g.:
+
+> mv ~/.parity/906a34e69aec8c0d /tmp
+> parity";
+
+/// TraceDB errors.
+pub enum Error {
+	/// Returned when tracing is enabled,
+	/// but database does not contain traces of old transactions.
+	ResyncRequired,
+}
+
+/// TODO: replace `Debug` with default implementation,
+/// once we stop using it to display errors to user.
+impl Debug for Error {
+	fn fmt(&self, f: &mut Formatter) -> Result<(), FmtError> {
+		write!(f, "{}", RESYNC_ERR)
+	}
+}
+
+impl Display for Error {
+	fn fmt(&self, f: &mut Formatter) -> Result<(), FmtError> {
+		write!(f, "{}", RESYNC_ERR)
+	}
+}
diff --git a/ethcore/src/trace/mod.rs b/ethcore/src/trace/mod.rs
index 01763a167..f51cf8ee5 100644
--- a/ethcore/src/trace/mod.rs
+++ b/ethcore/src/trace/mod.rs
@@ -20,6 +20,7 @@ mod block;
 mod bloom;
 mod config;
 mod db;
+mod error;
 mod executive_tracer;
 pub mod flat;
 mod import;
@@ -29,6 +30,7 @@ pub use types::trace_types::*;
 pub use self::block::BlockTraces;
 pub use self::config::{Config, Switch};
 pub use self::db::TraceDB;
+pub use self::error::Error;
 pub use types::trace_types::trace::Trace;
 pub use self::noop_tracer::NoopTracer;
 pub use self::executive_tracer::ExecutiveTracer;
diff --git a/rpc/src/v1/impls/eth.rs b/rpc/src/v1/impls/eth.rs
index 6fddf7b4f..8a12bbf61 100644
--- a/rpc/src/v1/impls/eth.rs
+++ b/rpc/src/v1/impls/eth.rs
@@ -28,7 +28,7 @@ use util::numbers::*;
 use util::sha3::*;
 use util::bytes::{ToPretty};
 use util::rlp::{encode, UntrustedRlp, View};
-use ethcore::client::*;
+use ethcore::client::{BlockChainClient, BlockId, TransactionId, UncleId};
 use ethcore::block::IsBlock;
 use ethcore::views::*;
 use ethcore::ethereum::Ethash;