diff --git a/miner/worker.go b/miner/worker.go
index 9afc65ab1..936a9e74a 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -628,7 +628,7 @@ func (w *worker) mainLoop() {
 				if gp := w.current.gasPool; gp != nil && gp.Gas() < params.TxGas {
 					continue
 				}
-				txs := make(map[common.Address]types.Transactions)
+				txs := make(map[common.Address]types.Transactions, len(ev.Txs))
 				for _, tx := range ev.Txs {
 					acc, _ := types.Sender(w.current.signer, tx)
 					txs[acc] = append(txs[acc], tx)