diff --git a/util/kvdb/src/lib.rs b/util/kvdb/src/lib.rs
index d10d663ba..b78ab1055 100644
--- a/util/kvdb/src/lib.rs
+++ b/util/kvdb/src/lib.rs
@@ -254,12 +254,12 @@ impl KeyValueDB for InMemory {
 		for op in ops {
 			match op {
 				DBOp::Insert { col, key, value } => {
-					if let Some(mut col) = columns.get_mut(&col) {
+					if let Some(col) = columns.get_mut(&col) {
 						col.insert(key.into_vec(), value);
 					}
 				},
 				DBOp::InsertCompressed { col, key, value } => {
-					if let Some(mut col) = columns.get_mut(&col) {
+					if let Some(col) = columns.get_mut(&col) {
 						let compressed = UntrustedRlp::new(&value).compress(RlpType::Blocks);
 						let mut value = DBValue::new();
 						value.append_slice(&compressed);
@@ -267,7 +267,7 @@ impl KeyValueDB for InMemory {
 					}
 				},
 				DBOp::Delete { col, key } => {
-					if let Some(mut col) = columns.get_mut(&col) {
+					if let Some(col) = columns.get_mut(&col) {
 						col.remove(&*key);
 					}
 				},
diff --git a/util/network/src/discovery.rs b/util/network/src/discovery.rs
index 4ff389b3c..6d8e906b7 100644
--- a/util/network/src/discovery.rs
+++ b/util/network/src/discovery.rs
@@ -156,7 +156,7 @@ impl Discovery {
 		trace!(target: "discovery", "Inserting {:?}", &e);
 		let id_hash = keccak(e.id);
 		let ping = {
-			let mut bucket = &mut self.node_buckets[Discovery::distance(&self.id_hash, &id_hash) as usize];
+			let bucket = &mut self.node_buckets[Discovery::distance(&self.id_hash, &id_hash) as usize];
 			let updated = if let Some(node) = bucket.nodes.iter_mut().find(|n| n.address.id == e.id) {
 				node.address = e.clone();
 				node.timeout = None;
@@ -169,7 +169,7 @@ impl Discovery {
 
 			if bucket.nodes.len() > BUCKET_SIZE {
 				//ping least active node
-				let mut last = bucket.nodes.back_mut().expect("Last item is always present when len() > 0");
+				let last = bucket.nodes.back_mut().expect("Last item is always present when len() > 0");
 				last.timeout = Some(time::precise_time_ns());
 				Some(last.address.endpoint.clone())
 			} else { None }
@@ -180,7 +180,7 @@ impl Discovery {
 	}
 
 	fn clear_ping(&mut self, id: &NodeId) {
-		let mut bucket = &mut self.node_buckets[Discovery::distance(&self.id_hash, &keccak(id)) as usize];
+		let bucket = &mut self.node_buckets[Discovery::distance(&self.id_hash, &keccak(id)) as usize];
 		if let Some(node) = bucket.nodes.iter_mut().find(|n| &n.address.id == id) {
 			node.timeout = None;
 		}
diff --git a/util/network/src/node_table.rs b/util/network/src/node_table.rs
index 052657db6..0b7725adc 100644
--- a/util/network/src/node_table.rs
+++ b/util/network/src/node_table.rs
@@ -253,7 +253,7 @@ impl NodeTable {
 	/// Apply table changes coming from discovery
 	pub fn update(&mut self, mut update: TableUpdates, reserved: &HashSet<NodeId>) {
 		for (_, node) in update.added.drain() {
-			let mut entry = self.nodes.entry(node.id.clone()).or_insert_with(|| Node::new(node.id.clone(), node.endpoint.clone()));
+			let entry = self.nodes.entry(node.id.clone()).or_insert_with(|| Node::new(node.id.clone(), node.endpoint.clone()));
 			entry.endpoint = node.endpoint;
 		}
 		for r in update.removed {
diff --git a/util/table/src/lib.rs b/util/table/src/lib.rs
index e84fce07d..bef453426 100644
--- a/util/table/src/lib.rs
+++ b/util/table/src/lib.rs
@@ -91,7 +91,7 @@ impl<Row, Col, Val> Table<Row, Col, Val>
 			if let None = row_map {
 				return None;
 			}
-			let mut row_map = row_map.unwrap();
+			let row_map = row_map.unwrap();
 			let val = row_map.remove(col);
 			(val, row_map.is_empty())
 		};