diff --git a/blacklist.go b/blacklist.go
new file mode 100644
index 0000000..17bb241
--- /dev/null
+++ b/blacklist.go
@@ -0,0 +1,28 @@
+package pubsub
+
+import (
+	peer "github.com/libp2p/go-libp2p-peer"
+)
+
+// Blacklist is an interface for peer blacklisting.
+type Blacklist interface {
+	Add(peer.ID)
+	Contains(peer.ID) bool
+}
+
+// MapBlacklist is a blacklist implementation using a perfect map
+type MapBlacklist map[peer.ID]struct{}
+
+// NewMapBlacklist creates a new MapBlacklist
+func NewMapBlacklist() Blacklist {
+	return MapBlacklist(make(map[peer.ID]struct{}))
+}
+
+func (b MapBlacklist) Add(p peer.ID) {
+	b[p] = struct{}{}
+}
+
+func (b MapBlacklist) Contains(p peer.ID) bool {
+	_, ok := b[p]
+	return ok
+}
diff --git a/pubsub.go b/pubsub.go
index 790db65..3c5cebe 100644
--- a/pubsub.go
+++ b/pubsub.go
@@ -99,7 +99,7 @@ type PubSub struct {
 	eval chan func()
 
 	// peer blacklist
-	blacklist     map[peer.ID]struct{}
+	blacklist     Blacklist
 	blacklistPeer chan peer.ID
 
 	peers        map[peer.ID]chan *RPC
@@ -183,7 +183,7 @@ func NewPubSub(ctx context.Context, h host.Host, rt PubSubRouter, opts ...Option
 		topics:           make(map[string]map[peer.ID]struct{}),
 		peers:            make(map[peer.ID]chan *RPC),
 		topicVals:        make(map[string]*topicVal),
-		blacklist:        make(map[peer.ID]struct{}),
+		blacklist:        NewMapBlacklist(),
 		blacklistPeer:    make(chan peer.ID),
 		seenMessages:     timecache.NewTimeCache(TimeCacheDuration),
 		counter:          uint64(time.Now().UnixNano()),
@@ -268,6 +268,15 @@ func WithStrictSignatureVerification(required bool) Option {
 	}
 }
 
+// WithBlacklist provides an implementation of the blacklist; the default is a
+// MapBlacklist
+func WithBlacklist(b Blacklist) Option {
+	return func(p *PubSub) error {
+		p.blacklist = b
+		return nil
+	}
+}
+
 // processLoop handles all inputs arriving on the channels
 func (p *PubSub) processLoop(ctx context.Context) {
 	defer func() {
@@ -282,14 +291,12 @@ func (p *PubSub) processLoop(ctx context.Context) {
 	for {
 		select {
 		case pid := <-p.newPeers:
-			_, ok := p.peers[pid]
-			if ok {
+			if p.blacklist.Contains(pid) {
 				log.Warning("already have connection to peer: ", pid)
 				continue
 			}
 
-			_, ok = p.blacklist[pid]
-			if ok {
+			if p.blacklist.Contains(pid) {
 				log.Warning("ignoring connection from blacklisted peer: ", pid)
 				continue
 			}
@@ -309,8 +316,7 @@ func (p *PubSub) processLoop(ctx context.Context) {
 				continue
 			}
 
-			_, ok = p.blacklist[pid]
-			if ok {
+			if p.blacklist.Contains(pid) {
 				log.Warning("closing stream for blacklisted peer: ", pid)
 				close(ch)
 				s.Reset()
@@ -396,7 +402,7 @@ func (p *PubSub) processLoop(ctx context.Context) {
 
 		case pid := <-p.blacklistPeer:
 			log.Infof("Blacklisting peer %s", pid)
-			p.blacklist[pid] = struct{}{}
+			p.blacklist.Add(pid)
 
 			ch, ok := p.peers[pid]
 			if ok {
@@ -602,13 +608,13 @@ func msgID(pmsg *pb.Message) string {
 // pushMsg pushes a message performing validation as necessary
 func (p *PubSub) pushMsg(vals []*topicVal, src peer.ID, msg *Message) {
 	// reject messages from blacklisted peers
-	if _, ok := p.blacklist[src]; ok {
+	if p.blacklist.Contains(src) {
 		log.Warningf("dropping message from blacklisted peer %s", src)
 		return
 	}
 
 	// even if they are forwarded by good peers
-	if _, ok := p.blacklist[msg.GetFrom()]; ok {
+	if p.blacklist.Contains(msg.GetFrom()) {
 		log.Warningf("dropping message from blacklisted source %s", src)
 		return
 	}