diff --git a/ethcore/src/json_tests/chain.rs b/ethcore/src/json_tests/chain.rs
index a5f5e36c9..2e538322c 100644
--- a/ethcore/src/json_tests/chain.rs
+++ b/ethcore/src/json_tests/chain.rs
@@ -41,20 +41,28 @@ pub fn json_chain_test(json_data: &[u8], era: ChainEra) -> Vec<String> {
 
 			flush!("   - {}...", name);
 
-			let mut spec = match era {
-				ChainEra::Frontier => ethereum::new_frontier_test(),
-				ChainEra::Homestead => ethereum::new_homestead_test(),
+			let spec = || {
+				let genesis = Genesis::from(blockchain.genesis());
+				let state = From::from(blockchain.pre_state.clone());
+				let mut spec = match era {
+					ChainEra::Frontier => ethereum::new_frontier_test(),
+					ChainEra::Homestead => ethereum::new_homestead_test(),
+				};
+				spec.set_genesis_state(state);
+				spec.overwrite_genesis_params(genesis);
+				assert!(spec.is_state_root_valid());
+				spec
 			};
 
-			let genesis = Genesis::from(blockchain.genesis());
-			let state = From::from(blockchain.pre_state.clone());
-			spec.set_genesis_state(state);
-			spec.overwrite_genesis_params(genesis);
-			assert!(spec.is_state_root_valid());
-
 			let temp = RandomTempPath::new();
 			{
-				let client = Client::new(ClientConfig::default(), spec.clone(), temp.as_path(), Arc::new(Miner::with_spec(spec)), IoChannel::disconnected()).unwrap();
+				let client = Client::new(
+					ClientConfig::default(),
+					spec(),
+					temp.as_path(),
+					Arc::new(Miner::with_spec(spec())),
+					IoChannel::disconnected()
+				).unwrap();
 				for b in &blockchain.blocks_rlp() {
 					if Block::is_good(&b) {
 						let _ = client.import_block(b.clone());
diff --git a/ethcore/src/miner/mod.rs b/ethcore/src/miner/mod.rs
index 91905ff4c..c9e725a4e 100644
--- a/ethcore/src/miner/mod.rs
+++ b/ethcore/src/miner/mod.rs
@@ -33,7 +33,7 @@
 //! use ethcore::miner::{Miner, MinerService};
 //!
 //! fn main() {
-//!		let miner: Miner = Miner::with_spec(ethereum::new_frontier());
+//!		let miner: Miner = Miner::with_spec(ethereum::new_frontier(true));
 //!		// get status
 //!		assert_eq!(miner.status().transactions_in_pending_queue, 0);
 //!