diff --git a/src/sync/chain.rs b/src/sync/chain.rs
index 95505ff81..bfbf3cfb8 100644
--- a/src/sync/chain.rs
+++ b/src/sync/chain.rs
@@ -386,31 +386,35 @@ impl ChainSync {
 		let h = header_rlp.as_raw().sha3();
 
 		trace!(target: "sync", "{} -> NewBlock ({})", peer_id, h);
-		match io.chain().import_block(block_rlp.as_raw()) {
-			ImportResult::AlreadyInChain => {
-				trace!(target: "sync", "New block already in chain {:?}", h);
-			},
-			ImportResult::AlreadyQueued(_) => {
-				trace!(target: "sync", "New block already queued {:?}", h);
-			},
-			ImportResult::Queued(QueueStatus::Known) => {
-				trace!(target: "sync", "New block queued {:?}", h);
-			},
-			ImportResult::Queued(QueueStatus::Unknown) => {
-				trace!(target: "sync", "New block unknown {:?}", h);
-				//TODO: handle too many unknown blocks
-				let difficulty: U256 = try!(r.val_at(1));
-				let peer_difficulty = self.peers.get_mut(&peer_id).expect("ChainSync: unknown peer").difficulty;
-				if difficulty > peer_difficulty {
-					trace!(target: "sync", "Received block {:?}  with no known parent. Peer needs syncing...", h);
-					self.sync_peer(io, peer_id, true);
+		let header_view = HeaderView::new(header_rlp.as_raw());
+		// TODO: Decompose block and add to self.headers and self.bodies instead
+		if header_view.number() == From::from(self.last_imported_block + 1) {
+			match io.chain().import_block(block_rlp.as_raw()) {
+				ImportResult::AlreadyInChain => {
+					trace!(target: "sync", "New block already in chain {:?}", h);
+				},
+				ImportResult::AlreadyQueued(_) => {
+					trace!(target: "sync", "New block already queued {:?}", h);
+				},
+				ImportResult::Queued(QueueStatus::Known) => {
+					trace!(target: "sync", "New block queued {:?}", h);
+				},
+				ImportResult::Queued(QueueStatus::Unknown) => {
+					trace!(target: "sync", "New block unknown {:?}", h);
+					//TODO: handle too many unknown blocks
+					let difficulty: U256 = try!(r.val_at(1));
+					let peer_difficulty = self.peers.get_mut(&peer_id).expect("ChainSync: unknown peer").difficulty;
+					if difficulty > peer_difficulty {
+						trace!(target: "sync", "Received block {:?}  with no known parent. Peer needs syncing...", h);
+						self.sync_peer(io, peer_id, true);
+					}
+				},
+				ImportResult::Bad =>{
+					debug!(target: "sync", "Bad new block {:?}", h);
+					io.disable_peer(peer_id);
 				}
-			},
-			ImportResult::Bad =>{
-				debug!(target: "sync", "Bad new block {:?}", h);
-				io.disable_peer(peer_id);
-			}
-		};
+			};
+		} 
 		Ok(())
 	}
 
diff --git a/src/sync/io.rs b/src/sync/io.rs
index 54bd22f14..ed7b0fec5 100644
--- a/src/sync/io.rs
+++ b/src/sync/io.rs
@@ -1,10 +1,11 @@
 use client::BlockChainClient;
-use util::network::{HandlerIo, PeerId, PacketId, Error as NetworkError};
+use util::network::{HandlerIo, PeerId, PacketId,};
+use util::error::UtilError;
 
 pub trait SyncIo {
 	fn disable_peer(&mut self, peer_id: &PeerId);
-	fn respond(&mut self, packet_id: PacketId, data: Vec<u8>) -> Result<(), NetworkError>;
-	fn send(&mut self, peer_id: PeerId, packet_id: PacketId, data: Vec<u8>) -> Result<(), NetworkError>;
+	fn respond(&mut self, packet_id: PacketId, data: Vec<u8>) -> Result<(), UtilError>;
+	fn send(&mut self, peer_id: PeerId, packet_id: PacketId, data: Vec<u8>) -> Result<(), UtilError>;
 	fn chain<'s>(&'s mut self) -> &'s mut BlockChainClient;
 }
 
@@ -27,11 +28,11 @@ impl<'s, 'h> SyncIo for NetSyncIo<'s, 'h> {
 		self.network.disable_peer(*peer_id);
 	}
 
-	fn respond(&mut self, packet_id: PacketId, data: Vec<u8>) -> Result<(), NetworkError>{
+	fn respond(&mut self, packet_id: PacketId, data: Vec<u8>) -> Result<(), UtilError>{
 		self.network.respond(packet_id, data)
 	}
 
-	fn send(&mut self, peer_id: PeerId, packet_id: PacketId, data: Vec<u8>) -> Result<(), NetworkError>{
+	fn send(&mut self, peer_id: PeerId, packet_id: PacketId, data: Vec<u8>) -> Result<(), UtilError>{
 		self.network.send(peer_id, packet_id, data)
 	}
 
diff --git a/src/sync/tests.rs b/src/sync/tests.rs
index 28e526aa9..dfcf75c8b 100644
--- a/src/sync/tests.rs
+++ b/src/sync/tests.rs
@@ -4,7 +4,8 @@ use util::hash::{H256, FixedHash};
 use util::uint::{U256};
 use util::sha3::Hashable;
 use util::rlp::{self, Rlp, RlpStream, View, Stream};
-use util::network::{PeerId, PacketId, Error as NetworkError};
+use util::network::{PeerId, PacketId};
+use util::error::UtilError;
 use client::{BlockChainClient, BlockStatus, BlockNumber, TreeRoute, BlockQueueStatus, BlockChainInfo, ImportResult, QueueStatus};
 use header::Header as BlockHeader;
 use sync::io::SyncIo;
@@ -195,7 +196,7 @@ impl<'p> SyncIo for TestIo<'p> {
 	fn disable_peer(&mut self, _peer_id: &PeerId) {
 	}
 
-	fn respond(&mut self, packet_id: PacketId, data: Vec<u8>) -> Result<(), NetworkError> {
+	fn respond(&mut self, packet_id: PacketId, data: Vec<u8>) -> Result<(), UtilError> {
 		self.queue.push_back(TestPacket {
 			data: data,
 			packet_id: packet_id,
@@ -204,7 +205,7 @@ impl<'p> SyncIo for TestIo<'p> {
 		Ok(())
 	}
 
-	fn send(&mut self, peer_id: PeerId, packet_id: PacketId, data: Vec<u8>) -> Result<(), NetworkError> {
+	fn send(&mut self, peer_id: PeerId, packet_id: PacketId, data: Vec<u8>) -> Result<(), UtilError> {
 		self.queue.push_back(TestPacket {
 			data: data,
 			packet_id: packet_id,