diff --git a/accounts/abi/bind/backends/simulated.go b/accounts/abi/bind/backends/simulated.go
index 400227c3a8..de81db1344 100644
--- a/accounts/abi/bind/backends/simulated.go
+++ b/accounts/abi/bind/backends/simulated.go
@@ -168,18 +168,18 @@ func (b *SimulatedBackend) TransactionReceipt(ctx context.Context, txHash common
 // blockchain. The isPending return value indicates whether the transaction has been
 // mined yet. Note that the transaction may not be part of the canonical chain even if
 // it's not pending.
-func (b *SimulatedBackend) TransactionByHash(ctx context.Context, txHash common.Hash) (tx *types.Transaction, isPending bool, err error) {
+func (b *SimulatedBackend) TransactionByHash(ctx context.Context, txHash common.Hash) (*types.Transaction, bool, error) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
 
-	tx = b.pendingBlock.Transaction(txHash)
+	tx := b.pendingBlock.Transaction(txHash)
 	if tx != nil {
 		return tx, true, nil
 	}
-
 	tx, _, _, _ = rawdb.ReadTransaction(b.database, txHash)
 	if tx != nil {
 		return tx, false, nil
 	}
-
 	return nil, false, ethereum.NotFound
 }
 
diff --git a/accounts/abi/bind/backends/simulated_test.go b/accounts/abi/bind/backends/simulated_test.go
index ac6e9e228a..bd75807d75 100644
--- a/accounts/abi/bind/backends/simulated_test.go
+++ b/accounts/abi/bind/backends/simulated_test.go
@@ -1,3 +1,19 @@
+// Copyright 2019 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
 package backends_test
 
 import (
diff --git a/accounts/abi/bind/base_test.go b/accounts/abi/bind/base_test.go
index 8adff8b59b..02caf457a4 100644
--- a/accounts/abi/bind/base_test.go
+++ b/accounts/abi/bind/base_test.go
@@ -1,3 +1,19 @@
+// Copyright 2019 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
 package bind_test
 
 import (