diff --git a/sync/src/chain.rs b/sync/src/chain.rs
index 3c31315f2..13158f95a 100644
--- a/sync/src/chain.rs
+++ b/sync/src/chain.rs
@@ -20,6 +20,7 @@ use ethcore::header::{BlockNumber, Header as BlockHeader};
 use ethcore::client::{BlockChainClient, BlockStatus};
 use range_collection::{RangeCollection, ToUsize, FromUsize};
 use ethcore::error::*;
+use ethcore::block::Block;
 use io::SyncIo;
 
 impl ToUsize for BlockNumber {
@@ -669,6 +670,12 @@ impl ChainSync {
 				block_rlp.append_raw(body.at(0).as_raw(), 1);
 				block_rlp.append_raw(body.at(1).as_raw(), 1);
 				let h = &headers.1[i].hash;
+				// Perform basic block verification 
+				if !Block::is_good(block_rlp.as_raw()) {
+					debug!(target: "sync", "Bad block rlp {:?} : {:?}", h, block_rlp.as_raw());
+					restart = true;
+					break;
+				}
 				match io.chain().import_block(block_rlp.out()) {
 					Err(ImportError::AlreadyInChain) => {
 						trace!(target: "sync", "Block already in chain {:?}", h);
diff --git a/sync/src/tests.rs b/sync/src/tests.rs
index 070ae566d..41516ef60 100644
--- a/sync/src/tests.rs
+++ b/sync/src/tests.rs
@@ -38,7 +38,11 @@ impl TestBlockChainClient {
 			header.number = n as BlockNumber;
 			let mut uncles = RlpStream::new_list(if empty {0} else {1});
 			if !empty {
-				uncles.append(&H256::from(&U256::from(n)));
+				let mut uncle_header = BlockHeader::new();
+				uncle_header.difficulty = From::from(n);
+				uncle_header.parent_hash = self.last_hash.read().unwrap().clone();
+				uncle_header.number = n as BlockNumber;
+				uncles.append(&uncle_header);
 				header.uncles_hash = uncles.as_raw().sha3();
 			}
 			let mut rlp = RlpStream::new_list(3);