diff --git a/lib/mix/tasks/docker.ex b/lib/mix/tasks/docker.ex
index 524bbad..7194663 100644
--- a/lib/mix/tasks/docker.ex
+++ b/lib/mix/tasks/docker.ex
@@ -41,3 +41,12 @@ defmodule Mix.Tasks.Docker.Shipit do
 
   defdelegate run(args), to: MixDocker, as: :shipit
 end
+
+defmodule Mix.Tasks.Docker.Customize do
+  use Mix.Task
+
+  @shortdoc "Copy & customize Dockerfiles"
+  @preferred_cli_env :prod
+
+  defdelegate run(args), to: MixDocker, as: :customize
+end
diff --git a/lib/mix_docker.ex b/lib/mix_docker.ex
index 7c80eb5..34ed5d5 100644
--- a/lib/mix_docker.ex
+++ b/lib/mix_docker.ex
@@ -57,6 +57,11 @@ defmodule MixDocker do
     publish(args)
   end
 
+  def customize([]) do
+    try_copy_dockerfile @dockerfile_build
+    try_copy_dockerfile @dockerfile_release
+  end
+
   defp git_head_sha do
     {sha, 0} = System.cmd "git", ["rev-parse", "HEAD"]
     String.slice(sha, 0, 10)
@@ -109,19 +114,12 @@ defmodule MixDocker do
     system! "docker", ["push", image]
   end
 
-
   defp with_dockerfile(name, fun) do
     if File.exists?(name) do
       fun.()
     else
-      app = Mix.Project.get.project[:app]
-
       try do
-        content = [@dockerfile_path, name]
-          |> Path.join
-          |> File.read!
-          |> String.replace("${APP}", to_string(app))
-        File.write!(name, content)
+        copy_dockerfile(name)
         fun.()
       after
         File.rm(name)
@@ -129,6 +127,23 @@ defmodule MixDocker do
     end
   end
 
+  defp copy_dockerfile(name) do
+    app = Mix.Project.get.project[:app]
+    content = [@dockerfile_path, name]
+      |> Path.join
+      |> File.read!
+      |> String.replace("${APP}", to_string(app))
+    File.write!(name, content)
+  end
+
+  defp try_copy_dockerfile(name) do
+    if File.exists?(name) do
+      Logger.warn("#{name} already exists")
+    else
+      copy_dockerfile(name)
+    end
+  end
+
   defp system(cmd, args) do
     Logger.debug "$ #{cmd} #{args |> Enum.join(" ")}"
     System.cmd(cmd, args, into: IO.stream(:stdio, :line))
diff --git a/test-app/.gitignore b/test-app/.gitignore
index be9a5a7..942862c 100644
--- a/test-app/.gitignore
+++ b/test-app/.gitignore
@@ -21,3 +21,5 @@ app.tar.gz
 /rel
 .dockerignore
 mix.lock
+Dockerfile.build
+Dockerfile.release
diff --git a/test-app/mix.exs b/test-app/mix.exs
index 87720cc..9c8fc23 100644
--- a/test-app/mix.exs
+++ b/test-app/mix.exs
@@ -16,8 +16,10 @@ defmodule App.Mixfile do
 
   defp deps do
     [
-      # can't use path since it will be unavailable inside docker container
-      {:mix_docker, github: "recruitee/mix_docker", branch: "master"}
+      case Mix.env do
+        :dev  -> {:mix_docker, path: ".."}
+        :prod -> {:mix_docker, github: "recruitee/mix_docker", branch: "master"}
+      end
     ]
   end
 end
diff --git a/test/mix_docker_test.exs b/test/mix_docker_test.exs
index 8448a92..8ed274a 100644
--- a/test/mix_docker_test.exs
+++ b/test/mix_docker_test.exs
@@ -39,4 +39,13 @@ defmodule MixDockerTest do
       mix "docker.release"
     end
   end
+
+  test "customize" do
+    inapp do
+      mix "docker.customize"
+
+      assert File.exists?("Dockerfile.build")
+      assert File.exists?("Dockerfile.release")
+    end
+  end
 end