lib/packetgen/packet.rb in packetgen-2.4.0 vs lib/packetgen/packet.rb in packetgen-2.5.0

@@ -1,10 +1,12 @@
 # coding: utf-8
 # This file is part of PacketGen
 # See https://github.com/sdaubert/packetgen for more informations
 # Copyright (C) 2016 Sylvain Daubert <[e-mail]>
 # This program is published under MIT license.
+
+# frozen_string_literal: true
 require 'pcaprub'
 
 module PacketGen
 
   # An object of type {Packet} handles a network packet. This packet may contain
@@ -375,10 +377,10 @@
       if prev_header
         bindings = prev_header.class.known_headers[header.class]
         if bindings.nil?
           bindings = prev_header.class.known_headers[header.class.superclass]
           if bindings.nil?
-            msg = "#{prev_header.class} knowns no layer association with #{header.protocol_name}. "
+            msg = "#{prev_header.class} knowns no layer association with #{header.protocol_name}. ".dup
             msg << "Try #{prev_header.class}.bind_layer(#{header.class}, "
             msg << "#{prev_header.method_name}_proto_field: "
             msg << "value_for_#{header.method_name})"
             raise ArgumentError, msg
           end