diff --git a/mempool/mempool.go b/mempool/mempool.go
index 31db159ff..0300c402a 100644
--- a/mempool/mempool.go
+++ b/mempool/mempool.go
@@ -101,16 +101,15 @@ func (mem *Mempool) CheckTx(tx types.Tx) (err error) {
 }
 
 // TMSP callback function
-func (mem *Mempool) resCb(req tmsp.Request, res tmsp.Response) {
-	switch res := res.(type) {
-	case tmsp.ResponseCheckTx:
-		reqCheckTx := req.(tmsp.RequestCheckTx)
-		if res.Code == tmsp.RetCodeOK {
+func (mem *Mempool) resCb(req *tmsp.Request, res *tmsp.Response) {
+	switch res.Type {
+	case tmsp.ResponseTypeCheckTx:
+		if tmsp.RetCode(res.Code) == tmsp.RetCodeOK {
 			mem.counter++
 			memTx := &mempoolTx{
 				counter: mem.counter,
 				height:  int64(mem.height),
-				tx:      reqCheckTx.TxBytes,
+				tx:      req.Data,
 			}
 			mem.txs.PushBack(memTx)
 		} else {
diff --git a/proxy/local_app_conn.go b/proxy/local_app_conn.go
index 7c428e3f0..b982c0621 100644
--- a/proxy/local_app_conn.go
+++ b/proxy/local_app_conn.go
@@ -32,8 +32,8 @@ func (app *localAppConn) Error() error {
 
 func (app *localAppConn) EchoAsync(msg string) {
 	app.Callback(
-		tmsp.RequestEcho{msg},
-		tmsp.ResponseEcho{msg},
+		tmsp.RequestEcho(msg),
+		tmsp.ResponseEcho(msg),
 	)
 }
 
@@ -46,8 +46,8 @@ func (app *localAppConn) SetOptionAsync(key string, value string) {
 	log := app.Application.SetOption(key, value)
 	app.mtx.Unlock()
 	app.Callback(
-		tmsp.RequestSetOption{key, value},
-		tmsp.ResponseSetOption{log},
+		tmsp.RequestSetOption(key, value),
+		tmsp.ResponseSetOption(log),
 	)
 }
 
@@ -56,8 +56,8 @@ func (app *localAppConn) AppendTxAsync(tx []byte) {
 	code, result, log := app.Application.AppendTx(tx)
 	app.mtx.Unlock()
 	app.Callback(
-		tmsp.RequestAppendTx{tx},
-		tmsp.ResponseAppendTx{code, result, log},
+		tmsp.RequestAppendTx(tx),
+		tmsp.ResponseAppendTx(code, result, log),
 	)
 }
 
@@ -66,8 +66,8 @@ func (app *localAppConn) CheckTxAsync(tx []byte) {
 	code, result, log := app.Application.CheckTx(tx)
 	app.mtx.Unlock()
 	app.Callback(
-		tmsp.RequestCheckTx{tx},
-		tmsp.ResponseCheckTx{code, result, log},
+		tmsp.RequestCheckTx(tx),
+		tmsp.ResponseCheckTx(code, result, log),
 	)
 }
 
@@ -76,8 +76,8 @@ func (app *localAppConn) GetHashAsync() {
 	hash, log := app.Application.GetHash()
 	app.mtx.Unlock()
 	app.Callback(
-		tmsp.RequestGetHash{},
-		tmsp.ResponseGetHash{hash, log},
+		tmsp.RequestGetHash(),
+		tmsp.ResponseGetHash(hash, log),
 	)
 }
 
diff --git a/state/execution.go b/state/execution.go
index cdfe2eceb..0f62b8366 100644
--- a/state/execution.go
+++ b/state/execution.go
@@ -60,14 +60,14 @@ func (s *State) execBlockOnProxyApp(evsw *events.EventSwitch, proxyAppConn proxy
 	var validTxs, invalidTxs = 0, 0
 
 	// Execute transactions and get hash
-	proxyCb := func(req tmsp.Request, res tmsp.Response) {
-		switch res := res.(type) {
-		case tmsp.ResponseAppendTx:
+	proxyCb := func(req *tmsp.Request, res *tmsp.Response) {
+		switch res.Type {
+		case tmsp.ResponseTypeAppendTx:
 			// TODO: make use of res.Log
 			// TODO: make use of this info
 			// Blocks may include invalid txs.
 			// reqAppendTx := req.(tmsp.RequestAppendTx)
-			if res.Code == tmsp.RetCodeOK {
+			if tmsp.RetCode(res.Code) == tmsp.RetCodeOK {
 				validTxs += 1
 			} else {
 				log.Debug("Invalid tx", "code", res.Code, "log", res.Log)