diff --git a/ethcore/src/client/client.rs b/ethcore/src/client/client.rs
index b8541470b..577829d45 100644
--- a/ethcore/src/client/client.rs
+++ b/ethcore/src/client/client.rs
@@ -25,6 +25,7 @@ use blockchain::{BlockReceipts, BlockChain, BlockChainDB, BlockProvider, TreeRou
 use bytes::Bytes;
 use call_contract::{CallContract, RegistryInfo};
 use ethcore_miner::pool::VerifiedTransaction;
+use ethcore_miner::service_transaction_checker::ServiceTransactionChecker;
 use ethereum_types::{H256, Address, U256};
 use evm::Schedule;
 use hash::keccak;
@@ -2156,11 +2157,16 @@ impl BlockChainClient for Client {
 
 	fn transact_contract(&self, address: Address, data: Bytes) -> Result<(), transaction::Error> {
 		let authoring_params = self.importer.miner.authoring_params();
+		let service_transaction_checker = ServiceTransactionChecker::default();
+		let gas_price = match service_transaction_checker.check_address(self, authoring_params.author) {
+			Ok(true) => U256::zero(),
+			_ => self.importer.miner.sensible_gas_price(),
+		};
 		let transaction = transaction::Transaction {
 			nonce: self.latest_nonce(&authoring_params.author),
 			action: Action::Call(address),
 			gas: self.importer.miner.sensible_gas_limit(),
-			gas_price: self.importer.miner.sensible_gas_price(),
+			gas_price,
 			value: U256::zero(),
 			data: data,
 		};
diff --git a/miner/src/service_transaction_checker.rs b/miner/src/service_transaction_checker.rs
index 17776f156..c9b3b4b23 100644
--- a/miner/src/service_transaction_checker.rs
+++ b/miner/src/service_transaction_checker.rs
@@ -20,6 +20,7 @@ use call_contract::{CallContract, RegistryInfo};
 use types::ids::BlockId;
 use types::transaction::SignedTransaction;
 use ethabi::FunctionOutputDecoder;
+use ethereum_types::Address;
 
 use_contract!(service_transaction, "res/contracts/service_transaction.json");
 
@@ -30,23 +31,24 @@ const SERVICE_TRANSACTION_CONTRACT_REGISTRY_NAME: &'static str = "service_transa
 pub struct ServiceTransactionChecker;
 
 impl ServiceTransactionChecker {
-	/// Checks if given address is whitelisted to send service transactions.
+	/// Checks if given address in tx is whitelisted to send service transactions.
 	pub fn check<C: CallContract + RegistryInfo>(&self, client: &C, tx: &SignedTransaction) -> Result<bool, String> {
 		let sender = tx.sender();
-		let hash = tx.hash();
-
 		// Skip checking the contract if the transaction does not have zero gas price
 		if !tx.gas_price.is_zero() {
 			return Ok(false)
 		}
 
-		let address = client.registry_address(SERVICE_TRANSACTION_CONTRACT_REGISTRY_NAME.to_owned(), BlockId::Latest)
+		self.check_address(client, sender)
+	}
+
+	/// Checks if given address is whitelisted to send service transactions.
+	pub fn check_address<C: CallContract + RegistryInfo>(&self, client: &C, sender: Address) -> Result<bool, String> {
+		let contract_address = client.registry_address(SERVICE_TRANSACTION_CONTRACT_REGISTRY_NAME.to_owned(), BlockId::Latest)
 			.ok_or_else(|| "contract is not configured")?;
-
-		trace!(target: "txqueue", "[{:?}] Checking service transaction checker contract from {}", hash, sender);
-
+		trace!(target: "txqueue", "Checking service transaction checker contract from {}", sender);
 		let (data, decoder) = service_transaction::functions::certified::call(sender);
-		let value = client.call_contract(BlockId::Latest, address, data)?;
+		let value = client.call_contract(BlockId::Latest, contract_address, data)?;
 		decoder.decode(&value).map_err(|e| e.to_string())
 	}
 }
diff --git a/rpc/src/v1/impls/personal.rs b/rpc/src/v1/impls/personal.rs
index 35a304df6..3bae576c0 100644
--- a/rpc/src/v1/impls/personal.rs
+++ b/rpc/src/v1/impls/personal.rs
@@ -20,8 +20,8 @@ use std::time::Duration;
 
 use bytes::Bytes;
 use ethcore::account_provider::AccountProvider;
-use types::transaction::PendingTransaction;
-use types::transaction::SignedTransaction;
+
+use types::transaction::{PendingTransaction, SignedTransaction};
 use ethereum_types::{H520, U128, Address};
 use ethkey::{public_to_address, recover, Signature};