diff --git a/consensus/common_test.go b/consensus/common_test.go
index fad0969bf..c942ac978 100644
--- a/consensus/common_test.go
+++ b/consensus/common_test.go
@@ -16,6 +16,7 @@ import (
 	sm "github.com/tendermint/tendermint/state"
 	"github.com/tendermint/tendermint/types"
 	tmspcli "github.com/tendermint/tmsp/client"
+	tmsp "github.com/tendermint/tmsp/types"
 
 	"github.com/tendermint/tmsp/example/counter"
 )
@@ -302,17 +303,17 @@ func fixedConsensusState() *ConsensusState {
 	state := sm.MakeGenesisStateFromFile(stateDB, config.GetString("genesis_file"))
 	privValidatorFile := config.GetString("priv_validator_file")
 	privValidator := types.LoadOrGenPrivValidator(privValidatorFile)
-	return newConsensusState(state, privValidator)
+	return newConsensusState(state, privValidator, counter.NewCounterApplication(true))
 
 }
 
-func newConsensusState(state *sm.State, pv *types.PrivValidator) *ConsensusState {
+func newConsensusState(state *sm.State, pv *types.PrivValidator, app tmsp.Application) *ConsensusState {
 	// Get BlockStore
 	blockDB := dbm.NewMemDB()
 	blockStore := bc.NewBlockStore(blockDB)
 
 	// one for mempool, one for consensus
-	mtx, app := new(sync.Mutex), counter.NewCounterApplication(false)
+	mtx := new(sync.Mutex)
 	proxyAppConnMem := tmspcli.NewLocalClient(mtx, app)
 	proxyAppConnCon := tmspcli.NewLocalClient(mtx, app)
 
@@ -335,7 +336,7 @@ func randConsensusState(nValidators int) (*ConsensusState, []*validatorStub) {
 
 	vss := make([]*validatorStub, nValidators)
 
-	cs := newConsensusState(state, privVals[0])
+	cs := newConsensusState(state, privVals[0], counter.NewCounterApplication(true))
 
 	for i := 0; i < nValidators; i++ {
 		vss[i] = NewValidatorStub(privVals[i])
diff --git a/consensus/mempool_test.go b/consensus/mempool_test.go
new file mode 100644
index 000000000..0bf789dfd
--- /dev/null
+++ b/consensus/mempool_test.go
@@ -0,0 +1,110 @@
+package consensus
+
+import (
+	"encoding/binary"
+	//	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/tendermint/tendermint/config/tendermint_test"
+	"github.com/tendermint/tendermint/types"
+	tmsp "github.com/tendermint/tmsp/types"
+
+	. "github.com/tendermint/go-common"
+)
+
+func init() {
+	tendermint_test.ResetConfig("consensus_mempool_test")
+}
+
+func TestTxConcurrentWithCommit(t *testing.T) {
+
+	state, privVals := randGenesisState(1, false, 10)
+	cs := newConsensusState(state, privVals[0], NewCounterApplication())
+	height, round := cs.Height, cs.Round
+	newBlockCh := subscribeToEvent(cs.evsw, "tester", types.EventStringNewBlock(), 1)
+
+	appendTxsRange := func(start, end int) {
+		// Append some txs.
+		for i := start; i < end; i++ {
+			txBytes := make([]byte, 8)
+			binary.BigEndian.PutUint64(txBytes, uint64(i))
+			err := cs.mempool.CheckTx(txBytes, nil)
+			if err != nil {
+				t.Fatal("Error after CheckTx: %v", err)
+			}
+			//	time.Sleep(time.Microsecond * time.Duration(rand.Int63n(3000)))
+		}
+	}
+
+	NTxs := 10000
+	go appendTxsRange(0, NTxs)
+
+	startTestRound(cs, height, round)
+	ticker := time.NewTicker(time.Second * 5)
+	for nTxs := 0; nTxs < NTxs; {
+		select {
+		case b := <-newBlockCh:
+			nTxs += b.(types.EventDataNewBlock).Block.Header.NumTxs
+		case <-ticker.C:
+			t.Fatal("Timed out waiting to commit blocks with transactions")
+		}
+	}
+}
+
+// CounterApplication that maintains a mempool state and resets it upon commit
+type CounterApplication struct {
+	txCount        int
+	mempoolTxCount int
+}
+
+func NewCounterApplication() *CounterApplication {
+	return &CounterApplication{}
+}
+
+func (app *CounterApplication) Info() string {
+	return Fmt("txs:%v", app.txCount)
+}
+
+func (app *CounterApplication) SetOption(key string, value string) (log string) {
+	return ""
+}
+
+func (app *CounterApplication) AppendTx(tx []byte) tmsp.Result {
+	return runTx(tx, &app.txCount)
+}
+
+func (app *CounterApplication) CheckTx(tx []byte) tmsp.Result {
+	return runTx(tx, &app.mempoolTxCount)
+}
+
+func runTx(tx []byte, countPtr *int) tmsp.Result {
+	count := *countPtr
+	tx8 := make([]byte, 8)
+	copy(tx8[len(tx8)-len(tx):], tx)
+	txValue := binary.BigEndian.Uint64(tx8)
+	if txValue != uint64(count) {
+		return tmsp.Result{
+			Code: tmsp.CodeType_BadNonce,
+			Data: nil,
+			Log:  Fmt("Invalid nonce. Expected %v, got %v", count, txValue),
+		}
+	}
+	*countPtr += 1
+	return tmsp.OK
+}
+
+func (app *CounterApplication) Commit() tmsp.Result {
+	app.mempoolTxCount = app.txCount
+	if app.txCount == 0 {
+		return tmsp.OK
+	} else {
+		hash := make([]byte, 8)
+		binary.BigEndian.PutUint64(hash, uint64(app.txCount))
+		return tmsp.NewResultOK(hash, "")
+	}
+}
+
+func (app *CounterApplication) Query(query []byte) tmsp.Result {
+	return tmsp.NewResultOK(nil, Fmt("Query is not supported"))
+}