diff --git a/lib/rackstash/message.rb b/lib/rackstash/message.rb
index 95a5b7d..786e218 100644
--- a/lib/rackstash/message.rb
+++ b/lib/rackstash/message.rb
@@ -83,7 +83,11 @@ module Rackstash
     end
 
     def dup_freeze(obj)
-      obj.frozen? ? obj : obj.dup.freeze
+      if obj.frozen?
+        obj
+      else
+        obj.dup.freeze rescue obj
+      end
     end
   end
 end
diff --git a/spec/rackstash/message_spec.rb b/spec/rackstash/message_spec.rb
index f099ce1..29f3f8a 100644
--- a/spec/rackstash/message_spec.rb
+++ b/spec/rackstash/message_spec.rb
@@ -26,6 +26,16 @@ describe Rackstash::Message do
 
       expect(message.message).to eq exception
     end
+
+    it 'attempts to dup non-frozen objects' do
+      rational = Rational(2, 3)
+      expect(rational).to_not be_frozen
+
+      message = Rackstash::Message.new(rational)
+
+      expect(message.message).to_not be_frozen
+      expect(message.message).to equal rational
+    end
   end
 
   describe '#severity' do