diff --git a/parity/cli/mod.rs b/parity/cli/mod.rs
index d33c58d9d..7fcdd2209 100644
--- a/parity/cli/mod.rs
+++ b/parity/cli/mod.rs
@@ -48,7 +48,7 @@ usage! {
 		flag_testnet: bool,
 		flag_import_geth_keys: bool,
 		flag_datadir: Option<String>,
-		flag_networkid: Option<usize>,
+		flag_networkid: Option<u64>,
 		flag_peers: Option<u16>,
 		flag_nodekey: Option<String>,
 		flag_nodiscover: bool,
@@ -122,7 +122,7 @@ usage! {
 			or |c: &Config| otry!(c.network).nat.clone(),
 		flag_allow_ips: String = "all",
 			or |c: &Config| otry!(c.network).allow_ips.clone(),
-		flag_network_id: Option<usize> = None,
+		flag_network_id: Option<u64> = None,
 			or |c: &Config| otry!(c.network).id.clone().map(Some),
 		flag_bootnodes: Option<String> = None,
 			or |c: &Config| otry!(c.network).bootnodes.clone().map(|vec| Some(vec.join(","))),
@@ -328,7 +328,7 @@ struct Network {
 	max_pending_peers: Option<u16>,
 	nat: Option<String>,
 	allow_ips: Option<String>,
-	id: Option<usize>,
+	id: Option<u64>,
 	bootnodes: Option<Vec<String>>,
 	discovery: Option<bool>,
 	node_key: Option<String>,
diff --git a/parity/configuration.rs b/parity/configuration.rs
index c4a54f747..37c699521 100644
--- a/parity/configuration.rs
+++ b/parity/configuration.rs
@@ -527,7 +527,7 @@ impl Configuration {
 		Ok(ret)
 	}
 
-	fn network_id(&self) -> Option<usize> {
+	fn network_id(&self) -> Option<u64> {
 		self.args.flag_network_id.or(self.args.flag_networkid)
 	}
 
diff --git a/parity/run.rs b/parity/run.rs
index 70c0b86f3..42a972000 100644
--- a/parity/run.rs
+++ b/parity/run.rs
@@ -70,7 +70,7 @@ pub struct RunCmd {
 	pub http_conf: HttpConfiguration,
 	pub ipc_conf: IpcConfiguration,
 	pub net_conf: NetworkConfiguration,
-	pub network_id: Option<usize>,
+	pub network_id: Option<u64>,
 	pub warp_sync: bool,
 	pub acc_conf: AccountsConfig,
 	pub gas_pricer: GasPricerConfig,
@@ -194,7 +194,7 @@ pub fn execute(cmd: RunCmd, logger: Arc<RotatingLogger>) -> Result<(), String> {
 	let mut sync_config = SyncConfig::default();
 	sync_config.network_id = match cmd.network_id {
 		Some(id) => id,
-		None => spec.network_id() as usize,
+		None => spec.network_id(),
 	};
 	if spec.subprotocol_name().len() != 3 {
 		warn!("Your chain specification's subprotocol length is not 3. Ignoring.");
diff --git a/rpc/src/v1/tests/helpers/sync_provider.rs b/rpc/src/v1/tests/helpers/sync_provider.rs
index 24be33417..8800d926a 100644
--- a/rpc/src/v1/tests/helpers/sync_provider.rs
+++ b/rpc/src/v1/tests/helpers/sync_provider.rs
@@ -23,7 +23,7 @@ use ethsync::{SyncProvider, SyncStatus, SyncState, PeerInfo, TransactionStats};
 /// TestSyncProvider config.
 pub struct Config {
 	/// Protocol version.
-	pub network_id: usize,
+	pub network_id: u64,
 	/// Number of peers.
 	pub num_peers: usize,
 }
diff --git a/sync/src/api.rs b/sync/src/api.rs
index cdab0983a..5613b77ff 100644
--- a/sync/src/api.rs
+++ b/sync/src/api.rs
@@ -44,7 +44,7 @@ pub struct SyncConfig {
 	/// Enable ancient block download.
 	pub download_old_blocks: bool,
 	/// Network ID
-	pub network_id: usize,
+	pub network_id: u64,
 	/// Main "eth" subprotocol name.
 	pub subprotocol_name: [u8; 3],
 	/// Fork block to check
diff --git a/sync/src/chain.rs b/sync/src/chain.rs
index bd312c9ee..2d53ad5ee 100644
--- a/sync/src/chain.rs
+++ b/sync/src/chain.rs
@@ -192,7 +192,7 @@ pub struct SyncStatus {
 	/// Syncing protocol version. That's the maximum protocol version we connect to.
 	pub protocol_version: u8,
 	/// The underlying p2p network version.
-	pub network_id: usize,
+	pub network_id: u64,
 	/// `BlockChain` height for the moment the sync started.
 	pub start_block_number: BlockNumber,
 	/// Last fully downloaded and imported block number (if any).
@@ -273,7 +273,7 @@ struct PeerInfo {
 	/// Peer chain genesis hash
 	genesis: H256,
 	/// Peer network id
-	network_id: usize,
+	network_id: u64,
 	/// Peer best block hash
 	latest_hash: H256,
 	/// Peer total difficulty if known
@@ -341,7 +341,7 @@ pub struct ChainSync {
 	/// Last propagated block number
 	last_sent_block_number: BlockNumber,
 	/// Network ID
-	network_id: usize,
+	network_id: u64,
 	/// Optional fork block to check
 	fork_block: Option<(BlockNumber, H256)>,
 	/// Snapshot downloader.