diff --git a/consensus/common_test.go b/consensus/common_test.go
index bf805e095..c59a6d969 100644
--- a/consensus/common_test.go
+++ b/consensus/common_test.go
@@ -332,7 +332,7 @@ func consensusLogger() log.Logger {
 	})
 }
 
-func randConsensusNet(nValidators int, testName string, tickerFunc func() TimeoutTicker, appFunc func() abci.Application) []*ConsensusState {
+func randConsensusNet(nValidators int, testName string, tickerFunc func() TimeoutTicker, appFunc func() abci.Application, configOpts ...func(*cfg.Config)) []*ConsensusState {
 	genDoc, privVals := randGenesisDoc(nValidators, false, 10)
 	css := make([]*ConsensusState, nValidators)
 	logger := consensusLogger()
@@ -342,6 +342,9 @@ func randConsensusNet(nValidators int, testName string, tickerFunc func() Timeou
 		state.SetLogger(logger.With("module", "state", "validator", i))
 		state.Save()
 		thisConfig := ResetConfig(Fmt("%s_%d", testName, i))
+		for _, opt := range configOpts {
+			opt(thisConfig)
+		}
 		ensureDir(path.Dir(thisConfig.Consensus.WalFile()), 0700) // dir for wal
 		css[i] = newConsensusStateWithConfig(thisConfig, state, privVals[i], appFunc())
 		css[i].SetLogger(logger.With("validator", i))
diff --git a/consensus/reactor.go b/consensus/reactor.go
index 72d731aca..fb25c68f6 100644
--- a/consensus/reactor.go
+++ b/consensus/reactor.go
@@ -1178,6 +1178,8 @@ const (
 	msgTypeHasVote      = byte(0x15)
 	msgTypeVoteSetMaj23 = byte(0x16)
 	msgTypeVoteSetBits  = byte(0x17)
+
+	msgTypeProposalHeartbeat = byte(0x20)
 )
 
 // ConsensusMessage is a message that can be sent and received on the ConsensusReactor
@@ -1194,6 +1196,7 @@ var _ = wire.RegisterInterface(
 	wire.ConcreteType{&HasVoteMessage{}, msgTypeHasVote},
 	wire.ConcreteType{&VoteSetMaj23Message{}, msgTypeVoteSetMaj23},
 	wire.ConcreteType{&VoteSetBitsMessage{}, msgTypeVoteSetBits},
+	wire.ConcreteType{&ProposalHeartbeatMessage{}, msgTypeProposalHeartbeat},
 )
 
 // DecodeMessage decodes the given bytes into a ConsensusMessage.
diff --git a/consensus/reactor_test.go b/consensus/reactor_test.go
index a1ab37026..b1f9a0a5b 100644
--- a/consensus/reactor_test.go
+++ b/consensus/reactor_test.go
@@ -7,9 +7,11 @@ import (
 	"time"
 
 	"github.com/tendermint/abci/example/dummy"
+	"github.com/tendermint/tmlibs/events"
+
+	cfg "github.com/tendermint/tendermint/config"
 	"github.com/tendermint/tendermint/p2p"
 	"github.com/tendermint/tendermint/types"
-	"github.com/tendermint/tmlibs/events"
 )
 
 func init() {
@@ -76,6 +78,35 @@ func TestReactor(t *testing.T) {
 	}, css)
 }
 
+// Ensure a testnet sends proposal heartbeats and makes blocks when there are txs
+func TestReactorProposalHeartbeats(t *testing.T) {
+	N := 4
+	css := randConsensusNet(N, "consensus_reactor_test", newMockTickerFunc(true), newCounter,
+		func(c *cfg.Config) {
+			c.Consensus.CreateEmptyBlocks = false
+		})
+	reactors, eventChans := startConsensusNet(t, css, N, false)
+	defer stopConsensusNet(reactors)
+	heartbeatChans := make([]chan interface{}, N)
+	for i := 0; i < N; i++ {
+		heartbeatChans[i] = subscribeToEvent(css[i].evsw, "tester", types.EventStringProposalHeartbeat(), 1)
+	}
+	// wait till everyone sends a proposal heartbeat
+	timeoutWaitGroup(t, N, func(wg *sync.WaitGroup, j int) {
+		<-heartbeatChans[j]
+		wg.Done()
+	}, css)
+
+	// send a tx
+	css[3].mempool.CheckTx([]byte{1, 2, 3}, nil)
+
+	// wait till everyone makes the first new block
+	timeoutWaitGroup(t, N, func(wg *sync.WaitGroup, j int) {
+		<-eventChans[j]
+		wg.Done()
+	}, css)
+}
+
 //-------------------------------------------------------------
 // ensure we can make blocks despite cycling a validator set
 
diff --git a/mempool/mempool.go b/mempool/mempool.go
index 6113910b7..9638baf26 100644
--- a/mempool/mempool.go
+++ b/mempool/mempool.go
@@ -277,7 +277,7 @@ func (mem *Mempool) resCbRecheck(req *abci.Request, res *abci.Response) {
 // TxsAvailable returns a channel which fires once for every height,
 // and only when transactions are available in the mempool.
 // NOTE: the returned channel may be nil if EnableTxsAvailable was not called.
-func (mem *Mempool) TxsAvailable() chan int {
+func (mem *Mempool) TxsAvailable() <-chan int {
 	return mem.txsAvailable
 }
 
diff --git a/mempool/mempool_test.go b/mempool/mempool_test.go
index 2e7a575cf..ee61a468b 100644
--- a/mempool/mempool_test.go
+++ b/mempool/mempool_test.go
@@ -28,7 +28,7 @@ func newMempoolWithApp(t *testing.T, cc proxy.ClientCreator) *Mempool {
 	return mempool
 }
 
-func ensureNoFire(t *testing.T, ch chan int, timeoutMS int) {
+func ensureNoFire(t *testing.T, ch <-chan int, timeoutMS int) {
 	timer := time.NewTimer(time.Duration(timeoutMS) * time.Millisecond)
 	select {
 	case <-ch:
@@ -37,7 +37,7 @@ func ensureNoFire(t *testing.T, ch chan int, timeoutMS int) {
 	}
 }
 
-func ensureFire(t *testing.T, ch chan int, timeoutMS int) {
+func ensureFire(t *testing.T, ch <-chan int, timeoutMS int) {
 	timer := time.NewTimer(time.Duration(timeoutMS) * time.Millisecond)
 	select {
 	case <-ch:
diff --git a/types/services.go b/types/services.go
index 0008b68e7..1805a0090 100644
--- a/types/services.go
+++ b/types/services.go
@@ -24,7 +24,7 @@ type Mempool interface {
 	Update(height int, txs Txs)
 	Flush()
 
-	TxsAvailable() chan int
+	TxsAvailable() <-chan int
 	EnableTxsAvailable()
 }
 
@@ -38,7 +38,7 @@ func (m MockMempool) CheckTx(tx Tx, cb func(*abci.Response)) error { return nil
 func (m MockMempool) Reap(n int) Txs                               { return Txs{} }
 func (m MockMempool) Update(height int, txs Txs)                   {}
 func (m MockMempool) Flush()                                       {}
-func (m MockMempool) TxsAvailable() chan int                       { return make(chan int) }
+func (m MockMempool) TxsAvailable() <-chan int                     { return make(chan int) }
 func (m MockMempool) EnableTxsAvailable()                          {}
 
 //------------------------------------------------------