diff --git a/dup.rb b/dup.rb
index f4aad91..e7d76f3 100755
--- a/dup.rb
+++ b/dup.rb
@@ -38,6 +38,7 @@ MAPPINGS = [
 	['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}],
 	['hostname', '--hostname'],
+	['shm_size', '--shm-size'],
 	['working_dir', '--workdir', lambda{|c,i| (wd=c.Config.WorkingDir) == i.Config.WorkingDir ? nil : wd}],
 	['init', '--init', lambda{|c,i| c.Config.Init}, {:type=>:switch}],
 	['image', nil, lambda{|c,i| c.Config.Image}],
@@ -96,6 +97,7 @@ def get_sample(name="container")
 		remove: false
 		stop_signal: SIGUSR1
 		stop_grace_period: 5
+		shm_size: 256M
 		
 		before_build:
 		  - "echo 'Starting build'"