diff --git a/core/tx_pool.go b/core/tx_pool.go
index 148638fd75..dd01bb3814 100644
--- a/core/tx_pool.go
+++ b/core/tx_pool.go
@@ -54,6 +54,10 @@ const (
 )
 
 var (
+	// ErrAlreadyKnown is returned if the transactions is already contained
+	// within the pool.
+	ErrAlreadyKnown = errors.New("already known")
+
 	// ErrInvalidSender is returned if the transaction contains an invalid signature.
 	ErrInvalidSender = errors.New("invalid sender")
 
@@ -673,7 +677,7 @@ func (pool *TxPool) add(tx *types.Transaction, local bool) (replaced bool, err e
 	if pool.all.Get(hash) != nil {
 		log.Trace("Discarding already known transaction", "hash", hash)
 		knownTxMeter.Mark(1)
-		return false, fmt.Errorf("known transaction: %x", hash)
+		return false, ErrAlreadyKnown
 	}
 	// If the transaction fails basic validation, discard it
 	if err := pool.validateTx(tx, local); err != nil {
@@ -921,7 +925,7 @@ func (pool *TxPool) addTxs(txs []*types.Transaction, local, sync bool) []error {
 	for i, tx := range txs {
 		// If the transaction is known, pre-set the error slot
 		if pool.all.Get(tx.Hash()) != nil {
-			errs[i] = fmt.Errorf("known transaction: %x", tx.Hash())
+			errs[i] = ErrAlreadyKnown
 			knownTxMeter.Mark(1)
 			continue
 		}
@@ -999,6 +1003,12 @@ func (pool *TxPool) Get(hash common.Hash) *types.Transaction {
 	return pool.all.Get(hash)
 }
 
+// Has returns an indicator whether txpool has a transaction cached with the
+// given hash.
+func (pool *TxPool) Has(hash common.Hash) bool {
+	return pool.all.Get(hash) != nil
+}
+
 // removeTx removes a single transaction from the queue, moving all subsequent
 // transactions back to the future queue.
 func (pool *TxPool) removeTx(hash common.Hash, outofbound bool) {