diff --git a/src/syscall/zx/fidl/message.go b/src/syscall/zx/fidl/message.go
index bdbdf2b..f4f16c0 100644
--- a/src/syscall/zx/fidl/message.go
+++ b/src/syscall/zx/fidl/message.go
@@ -54,6 +54,9 @@
 // that is, header and payload.
 func MarshalMessage(header *MessageHeader, s Payload, data []byte, handles []zx.Handle) (int, int, error) {
 	MarshalHeader(header, data[:MessageHeaderSize])
+	if s == nil {
+		return MessageHeaderSize, 0, nil
+	}
 	// TODO(pascallouis): switch to MarshalNew when ready.
 	nb, nh, err := Marshal(s, data[MessageHeaderSize:], handles[:])
 	return nb + MessageHeaderSize, nh, err
@@ -65,6 +68,9 @@
 	if err := UnmarshalHeader(data[:MessageHeaderSize], header); err != nil {
 		return err
 	}
+	if s == nil {
+		return nil
+	}
 	// TODO(pascallouis): switch to MarshalNew when ready.
 	return Unmarshal(data[MessageHeaderSize:], handles[:], s)
 }