diff --git a/def.go b/def.go
index 254b2d5..1bf02ab 100644
--- a/def.go
+++ b/def.go
@@ -58,7 +58,7 @@ type PacketAdminJoin struct {
 
 func (p *PacketAdminJoin) Bytes() []byte {
 	buf := new(bytes.Buffer)
-	p.PLength = binary.Size(p)
+	p.PLength = uint16(binary.Size(p))
 	_ = binary.Write(buf, binary.LittleEndian, p)
 	return buf.Bytes()
 }