diff --git a/mempool/mempool.go b/mempool/mempool.go
index 1ed718091..935dfaac7 100644
--- a/mempool/mempool.go
+++ b/mempool/mempool.go
@@ -77,7 +77,7 @@ type Mempool struct {
 
 	// Keep a cache of already-seen txs.
 	// This reduces the pressure on the proxyApp.
-	cache *txCache
+	cache txCache
 
 	// A log of mempool txs
 	wal *auto.AutoFile
@@ -97,7 +97,11 @@ func NewMempool(config *cfg.MempoolConfig, proxyAppConn proxy.AppConnMempool, he
 		recheckCursor: nil,
 		recheckEnd:    nil,
 		logger:        log.NewNopLogger(),
-		cache:         newTxCache(config.CacheSize),
+	}
+	if config.CacheSize > 0 {
+		mempool.cache = newMapTxCache(config.CacheSize)
+	} else {
+		mempool.cache = nopTxCache{}
 	}
 	proxyAppConn.SetResponseCallback(mempool.resCb)
 	return mempool
@@ -448,41 +452,45 @@ func (memTx *mempoolTx) Height() int64 {
 
 //--------------------------------------------------------------------------------
 
-// txCache maintains a cache of transactions.
-type txCache struct {
+type txCache interface {
+	Reset()
+	Push(tx types.Tx) bool
+	Remove(tx types.Tx)
+}
+
+// mapTxCache maintains a cache of transactions.
+type mapTxCache struct {
 	mtx  sync.Mutex
 	size int
 	map_ map[string]struct{}
 	list *list.List // to remove oldest tx when cache gets too big
 }
 
-// newTxCache returns a new txCache.
-func newTxCache(cacheSize int) *txCache {
-	return &txCache{
+var _ txCache = (*mapTxCache)(nil)
+
+// newMapTxCache returns a new mapTxCache.
+func newMapTxCache(cacheSize int) *mapTxCache {
+	return &mapTxCache{
 		size: cacheSize,
 		map_: make(map[string]struct{}, cacheSize),
 		list: list.New(),
 	}
 }
 
-// Reset resets the txCache to empty.
-func (cache *txCache) Reset() {
+// Reset resets the cache to an empty state.
+func (cache *mapTxCache) Reset() {
 	cache.mtx.Lock()
 	cache.map_ = make(map[string]struct{}, cache.size)
 	cache.list.Init()
 	cache.mtx.Unlock()
 }
 
-// Push adds the given tx to the txCache. It returns false if tx is already in the cache.
-func (cache *txCache) Push(tx types.Tx) bool {
+// Push adds the given tx to the cache and returns true. It returns false if tx
+// is already in the cache.
+func (cache *mapTxCache) Push(tx types.Tx) bool {
 	cache.mtx.Lock()
 	defer cache.mtx.Unlock()
 
-	// if cache size is 0, do nothing
-	if cache.size == 0 {
-		return true
-	}
-
 	if _, exists := cache.map_[string(tx)]; exists {
 		return false
 	}
@@ -501,8 +509,16 @@ func (cache *txCache) Push(tx types.Tx) bool {
 }
 
 // Remove removes the given tx from the cache.
-func (cache *txCache) Remove(tx types.Tx) {
+func (cache *mapTxCache) Remove(tx types.Tx) {
 	cache.mtx.Lock()
 	delete(cache.map_, string(tx))
 	cache.mtx.Unlock()
 }
+
+type nopTxCache struct{}
+
+var _ txCache = (*nopTxCache)(nil)
+
+func (nopTxCache) Reset()             {}
+func (nopTxCache) Push(types.Tx) bool { return true }
+func (nopTxCache) Remove(types.Tx)    {}
diff --git a/mempool/reactor.go b/mempool/reactor.go
index d60852fde..5d1f4e793 100644
--- a/mempool/reactor.go
+++ b/mempool/reactor.go
@@ -6,7 +6,7 @@ import (
 	"time"
 
 	abci "github.com/tendermint/abci/types"
-	"github.com/tendermint/go-amino"
+	amino "github.com/tendermint/go-amino"
 	"github.com/tendermint/tmlibs/clist"
 	"github.com/tendermint/tmlibs/log"