diff --git a/dup.rb b/dup.rb
index f1cf954..cbc1de3 100755
--- a/dup.rb
+++ b/dup.rb
@@ -22,6 +22,7 @@ MAPPINGS = [
 	['stop_grace_period', '--stop-timeout', lambda{|c,i| c.Config.StopTimeout}],
 	['devices', '--device'],
 	['net', '--net'],
+	['ipv6', '--ipv6'],
 	['networks', '--network', lambda{|c,i| c.NetworkSettings.Networks.to_h.keys.map(&:to_s)}, {:type=>:hidden}],
 	['entrypoint', '--entrypoint', lambda{|c,i| (ep=c.Config.Entrypoint) == i.Config.Entrypoint ? nil : ep}, {:allow_empty=>true}],
 	['labels', '--label', lambda{|c,i| l=Hash[c.Config.Labels.to_h.delete_if{|k,v| i.Config.Labels[k]==v rescue false}.map{|k,v| [k.to_s, v]}] ; l}],