diff --git a/http3/server.go b/http3/server.go
index 7d2abffb..9ae1efe2 100644
--- a/http3/server.go
+++ b/http3/server.go
@@ -25,7 +25,7 @@ var (
 	quicListenAddr = quic.ListenAddrEarly
 )
 
-const nextProtoH3 = "h3-27"
+const nextProtoH3 = "h3-28"
 
 // contextKey is a value for use with context.WithValue. It's used as
 // a pointer so it fits in an interface{} without allocation.
diff --git a/interop/http09/server.go b/interop/http09/server.go
index 893fdbb0..a384e18c 100644
--- a/interop/http09/server.go
+++ b/interop/http09/server.go
@@ -16,7 +16,7 @@ import (
 	"github.com/lucas-clemente/quic-go"
 )
 
-const h09alpn = "hq-27"
+const h09alpn = "hq-28"
 
 type responseWriter struct {
 	io.Writer