diff --git a/net/resolve.go b/net/resolve.go
index a2478e7..532fa87 100644
--- a/net/resolve.go
+++ b/net/resolve.go
@@ -7,26 +7,26 @@ import (
 )
 
 // ResolveUnspecifiedAddress expands an unspecified ip addresses (/ip4/0.0.0.0, /ip6/::) to
-// use the known local interfaces. If ifaceAddr is nil, we request interface addresses
-// from the network stack. (this is so you can provide a cached value if resolving many addrs)
+// use the known local interfaces
 func ResolveUnspecifiedAddress(resolve ma.Multiaddr, ifaceAddrs []ma.Multiaddr) ([]ma.Multiaddr, error) {
-	// split address into its components
-	split := ma.Split(resolve)
-
 	// if first component (ip) is not unspecified, use it as is.
-	if !IsIPUnspecified(split[0]) {
+	first, rest := ma.SplitFirst(resolve)
+	if first == nil || !IsIPUnspecified(first) {
 		return []ma.Multiaddr{resolve}, nil
 	}
 
 	out := make([]ma.Multiaddr, 0, len(ifaceAddrs))
 	for _, ia := range ifaceAddrs {
-		// must match the first protocol to be resolve.
-		if ia.Protocols()[0].Code != resolve.Protocols()[0].Code {
+		// must match the first protocol to resolve.
+		match := false
+		ma.ForEach(ia, func(c ma.Component) bool {
+			match = c.Protocol().Code == first.Protocol().Code
+			return false
+		})
+		if !match {
 			continue
 		}
-
-		split[0] = ia
-		joined := ma.Join(split...)
+		joined := ma.Join(ia, rest)
 		out = append(out, joined)
 	}
 	if len(out) < 1 {
diff --git a/net/resolve_test.go b/net/resolve_test.go
index 387e70a..b1e2479 100644
--- a/net/resolve_test.go
+++ b/net/resolve_test.go
@@ -1,6 +1,7 @@
 package manet
 
 import (
+	"math/rand"
 	"testing"
 
 	ma "github.com/multiformats/go-multiaddr"
@@ -55,3 +56,17 @@ func TestResolvingAddrs(t *testing.T) {
 		t.Fatal("should have failed")
 	}
 }
+
+func BenchmarkResolveAddr(b *testing.B) {
+	b.ReportAllocs()
+	unspec := []ma.Multiaddr{
+		ma.StringCast("/ip4/0.0.0.0/tcp/1234"),
+	}
+
+	iface := []ma.Multiaddr{
+		ma.StringCast("/ip4/127.0.0.1"),
+	}
+	for i := 0; i < b.N; i++ {
+		ResolveUnspecifiedAddress(unspec[rand.Intn(len(unspec))], iface)
+	}
+}
diff --git a/util.go b/util.go
index cf4469a..71bddc7 100644
--- a/util.go
+++ b/util.go
@@ -27,16 +27,14 @@ func Join(ms ...Multiaddr) Multiaddr {
 	}
 
 	length := 0
-	bs := make([][]byte, len(ms))
-	for i, m := range ms {
-		bs[i] = m.Bytes()
-		length += len(bs[i])
+	for _, m := range ms {
+		length += len(m.Bytes())
 	}
 
 	bidx := 0
 	b := make([]byte, length)
-	for _, mb := range bs {
-		bidx += copy(b[bidx:], mb)
+	for _, m := range ms {
+		bidx += copy(b[bidx:], m.Bytes())
 	}
 	return &multiaddr{bytes: b}
 }