diff --git a/miner/src/miner.rs b/miner/src/miner.rs
index d03fcd524..f159cac1c 100644
--- a/miner/src/miner.rs
+++ b/miner/src/miner.rs
@@ -420,7 +420,7 @@ impl MinerService for Miner {
 
 	fn transaction(&self, hash: &H256) -> Option<SignedTransaction> {
 		match (self.sealing_enabled.load(atomic::Ordering::Relaxed), self.sealing_work.lock().unwrap().peek_last_ref()) {
-			(true, Some(pending)) => pending.transactions().iter().find(|t| &t.hash() == hash).map(|t| t.clone()),
+			(true, Some(pending)) => pending.transactions().iter().find(|t| &t.hash() == hash).cloned(),
 			_ => {
 				let queue = self.transaction_queue.lock().unwrap();
 				queue.find(hash)
diff --git a/parity/informant.rs b/parity/informant.rs
index c69c8938e..0eaebe10f 100644
--- a/parity/informant.rs
+++ b/parity/informant.rs
@@ -75,6 +75,7 @@ impl Informant {
 		}
 	}
 
+	#[cfg_attr(feature="dev", allow(match_bool))]
 	pub fn tick(&self, client: &Client, maybe_sync: Option<&EthSync>) {
 		let elapsed = self.last_tick.read().unwrap().elapsed();
 		if elapsed < Duration::from_secs(5) {
diff --git a/rpc/src/v1/impls/eth.rs b/rpc/src/v1/impls/eth.rs
index 4a4ee1643..a13512357 100644
--- a/rpc/src/v1/impls/eth.rs
+++ b/rpc/src/v1/impls/eth.rs
@@ -672,18 +672,26 @@ impl<C, M> EthFilter for EthFilterClient<C, M> where
 							to_value(&hashes)
 						},
 						PollFilter::PendingTransaction(ref mut previous_hashes) => {
+							// get hashes of pending transactions
 							let current_hashes = take_weak!(self.miner).pending_transactions_hashes();
-							// calculate diff
-							let previous_hashes_set = previous_hashes.into_iter().map(|h| h.clone()).collect::<HashSet<H256>>();
-							let diff = current_hashes
-								.iter()
-								.filter(|hash| previous_hashes_set.contains(&hash))
-								.cloned()
-								.collect::<Vec<H256>>();
 
+							let new_hashes =
+							{
+								let previous_hashes_set = previous_hashes.iter().collect::<HashSet<_>>();
+
+								//	find all new hashes
+								current_hashes
+									.iter()
+									.filter(|hash| !previous_hashes_set.contains(hash))
+									.cloned()
+									.collect::<Vec<H256>>()
+							};
+
+							// save all hashes of pending transactions
 							*previous_hashes = current_hashes;
 
-							to_value(&diff)
+							// return new hashes
+							to_value(&new_hashes)
 						},
 						PollFilter::Logs(ref mut block_number, ref mut previous_logs, ref filter) => {
 							// retrive the current block number
diff --git a/util/src/migration/db_impl.rs b/util/src/migration/db_impl.rs
index 02c66d19b..760babe3c 100644
--- a/util/src/migration/db_impl.rs
+++ b/util/src/migration/db_impl.rs
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
-//! kvdb::Database as migration::Destination
+//! `kvdb::Database` as `migration::Destination`
 
 use std::collections::BTreeMap;
 use kvdb::{Database, DBTransaction};