diff --git a/lib/net/dns/header.rb b/lib/net/dns/header.rb
index 37becb0..dba058b 100644
--- a/lib/net/dns/header.rb
+++ b/lib/net/dns/header.rb
@@ -113,10 +113,10 @@ class RCode
         # Constant for +rcode+ Response Code Refused Error
         REFUSED = 5
 
-        RCodeType = %w[NoError FormErr ServFail NXDomain NotImp
-                       Refused YXDomain YXRRSet NXRRSet NotAuth NotZone].freeze
+        RCodeType = Ractor.make_shareable(%w[NoError FormErr ServFail NXDomain NotImp
+                       Refused YXDomain YXRRSet NXRRSet NotAuth NotZone].freeze)
 
-        RCodeErrorString = ["No errors",
+        RCodeErrorString = Ractor.make_shareable(["No errors",
                             "The name server was unable to interpret the query",
                             "The name server was unable to process this query due to problem with the name server",
                             "Domain name referenced in the query does not exists",
@@ -126,7 +126,7 @@ class RCode
                             "",
                             "",
                             "",
-                            "",].freeze
+                            "",].freeze)
 
         attr_reader :code
         attr_reader :type
@@ -152,7 +152,7 @@ def to_s
       # Constant for +opCode+ status
       STATUS  = 2
       # Array with given strings
-      OPARR = %w[QUERY IQUERY STATUS].freeze
+      OPARR = Ractor.make_shareable(%w[QUERY IQUERY STATUS].freeze)
 
       # Reader for +id+ attribute
       attr_reader :id