diff --git a/ethcore/src/miner/miner.rs b/ethcore/src/miner/miner.rs
index 4b7671946..b8621a741 100644
--- a/ethcore/src/miner/miner.rs
+++ b/ethcore/src/miner/miner.rs
@@ -736,7 +736,7 @@ impl MinerService for Miner {
 
 				let sender = t.sender();
 				let balance = state.balance(&sender).map_err(ExecutionError::from)?;
-				let needed_balance = t.value + t.gas * t.gas_price;
+				let needed_balance = t.value.saturating_add(t.gas.saturating_mul(t.gas_price));
 				if balance < needed_balance {
 					// give the sender a sufficient balance
 					state.add_balance(&sender, &(needed_balance - balance), CleanupMode::NoEmpty)
diff --git a/rpc/src/v1/helpers/fake_sign.rs b/rpc/src/v1/helpers/fake_sign.rs
index c5b95f6a4..4300468ab 100644
--- a/rpc/src/v1/helpers/fake_sign.rs
+++ b/rpc/src/v1/helpers/fake_sign.rs
@@ -31,7 +31,7 @@ pub fn sign_call<B: MiningBlockChainClient, M: MinerService>(
 	gas_cap: bool,
 ) -> Result<SignedTransaction, Error> {
 	let from = request.from.unwrap_or(0.into());
-	let mut gas = request.gas.unwrap_or(U256::max_value());
+	let mut gas = request.gas.unwrap_or(U256::from(2) << 50);
 	if gas_cap {
 		let max_gas = 50_000_000.into();
 		if gas > max_gas {