diff --git a/hkexnet/consts.go b/hkexnet/consts.go
index 0916090..cd90130 100644
--- a/hkexnet/consts.go
+++ b/hkexnet/consts.go
@@ -11,6 +11,7 @@ package hkexnet
 //
 // Specified (in string form) as the extensions parameter
 // to hkexnet.Dial()
+// Alg is sent in a uint8 so there are up to 256 possible
 const (
 	KEX_HERRADURA256 = iota // this MUST be first for default if omitted in ctor
 	KEX_HERRADURA512
diff --git a/hkexnet/hkexnet.go b/hkexnet/hkexnet.go
index a085a12..a4e4a65 100644
--- a/hkexnet/hkexnet.go
+++ b/hkexnet/hkexnet.go
@@ -213,7 +213,7 @@ func _new(kexAlg KEXAlg, conn *net.Conn) (hc *Conn, e error) {
 		log.Printf("[KEx alg %d accepted]\n", kexAlg)
 	default:
 		// UNREACHABLE: _getkexalgnum() guarantees a valid KEX value
-		hc.kex = KEX_HERRADURA256
+		hc.kex = KEX_HERRADURA512
 		log.Printf("[KEx alg %d ?? defaults to %d]\n", kexAlg, hc.kex)
 	}
 	return
@@ -273,7 +273,7 @@ func (hc *Conn) applyConnExtensions(extensions ...string) {
 }
 
 func getkexalgnum(extensions ...string) (k KEXAlg) {
-	k = KEX_HERRADURA256 // default
+	k = KEX_HERRADURA512 // default
 	for _, s := range extensions {
 		switch s {
 		case "KEX_HERRADURA256":