diff --git a/xds/internal/clients/grpctransport/grpc_transport.go b/xds/internal/clients/grpctransport/grpc_transport.go
index af39349e9bae..a70faaba9005 100644
--- a/xds/internal/clients/grpctransport/grpc_transport.go
+++ b/xds/internal/clients/grpctransport/grpc_transport.go
@@ -211,6 +211,8 @@ func (s *stream) Recv() ([]byte, error) {
 	return typedRes, nil
 }
 
+// byteCodec here is still sending proto messages. It's just they are
+// in []byte form.
 type byteCodec struct{}
 
 func (c *byteCodec) Marshal(v any) ([]byte, error) {
@@ -229,5 +231,7 @@ func (c *byteCodec) Unmarshal(data []byte, v any) error {
 }
 
 func (c *byteCodec) Name() string {
-	return "grpctransport.byteCodec"
+	// Return "proto" to ensure the Content-Type header is "application/grpc",
+	// which is expected by standard gRPC servers for protobuf messages.
+	return "proto"
 }