diff --git a/repo2docker/app.py b/repo2docker/app.py
index c39b463b..f98184fb 100644
--- a/repo2docker/app.py
+++ b/repo2docker/app.py
@@ -149,6 +149,16 @@ class Repo2Docker(Application):
         """
         return pwd.getpwuid(os.getuid()).pw_name
 
+    appendix = Unicode(
+        config=True,
+        help="""
+        Appendix of Dockerfile commands to run at the end of the build.
+
+        Can be used to customize the resulting image after all
+        standard build steps finish.
+        """
+    )
+
     def fetch(self, url, ref, checkout_path):
         try:
             for line in execute_cmd(['git', 'clone', '--recursive', url, checkout_path],
@@ -309,6 +319,11 @@ class Repo2Docker(Application):
             default=[]
         )
 
+        argparser.add_argument(
+            '--appendix',
+            type=str,
+            help=self.traits()['appendix'].help,
+        )
         return argparser
 
     def json_excepthook(self, etype, evalue, traceback):
@@ -329,6 +344,8 @@ class Repo2Docker(Application):
             self.log_level = logging.DEBUG
 
         self.load_config_file(args.config)
+        if args.appendix:
+            self.appendix = args.appendix
 
         if os.path.exists(args.repo):
             # Let's treat this as a local directory we are building
@@ -559,6 +576,8 @@ class Repo2Docker(Application):
             else:
                 picked_buildpack = self.default_buildpack()
 
+            picked_buildpack.appendix = self.appendix
+
             self.log.debug(picked_buildpack.render(),
                            extra=dict(phase='building'))
 
diff --git a/repo2docker/buildpacks/base.py b/repo2docker/buildpacks/base.py
index 6dd8839b..d2b73e18 100644
--- a/repo2docker/buildpacks/base.py
+++ b/repo2docker/buildpacks/base.py
@@ -112,6 +112,11 @@ USER ${NB_USER}
 RUN ./{{ s }}
 {% endfor %}
 {% endif -%}
+
+{% if appendix -%}
+# Appendix:
+{{ appendix }}
+{% endif %}
 """
 
 DOC_URL = "http://repo2docker.readthedocs.io/en/latest/samples.html"
@@ -136,6 +141,7 @@ class BuildPack:
 
     def __init__(self):
         self.log = logging.getLogger('repo2docker')
+        self.appendix = ''
 
     def get_packages(self):
         """
@@ -309,6 +315,7 @@ class BuildPack:
             build_script_files=self.get_build_script_files(),
             base_packages=sorted(self.get_base_packages()),
             post_build_scripts=self.get_post_build_scripts(),
+            appendix=self.appendix,
         )
 
     def build(self, image_spec, memory_limit, build_args):
diff --git a/repo2docker/buildpacks/docker.py b/repo2docker/buildpacks/docker.py
index 8baa5dfb..4361ed6d 100644
--- a/repo2docker/buildpacks/docker.py
+++ b/repo2docker/buildpacks/docker.py
@@ -15,7 +15,7 @@ class DockerBuildPack(BuildPack):
     def render(self):
         Dockerfile = self.binder_path('Dockerfile')
         with open(Dockerfile) as f:
-            return f.read()
+            return '\n'.join([f.read(), self.appendix, ''])
 
     def build(self, image_spec, memory_limit, build_args):
         limits = {
diff --git a/repo2docker/buildpacks/legacy.py b/repo2docker/buildpacks/legacy.py
index afa683d6..8f5ad838 100644
--- a/repo2docker/buildpacks/legacy.py
+++ b/repo2docker/buildpacks/legacy.py
@@ -8,7 +8,7 @@ class LegacyBinderDockerBuildPack(DockerBuildPack):
 
     dockerfile = '._binder.Dockerfile'
 
-    dockerfile_appendix = dedent(r"""
+    legacy_appendix = dedent(r"""
     USER root
     COPY . /home/main/notebooks
     RUN chown -R main:main /home/main/notebooks
@@ -27,7 +27,7 @@ class LegacyBinderDockerBuildPack(DockerBuildPack):
 
     def render(self):
         with open('Dockerfile') as f:
-            return f.read() + self.dockerfile_appendix
+            return '\n'.join([f.read(), self.legacy_appendix, self.appendix, ''])
 
     def build(self, image_spec, memory_limit, build_args):
         with open(self.dockerfile, 'w') as f:
diff --git a/tests/conftest.py b/tests/conftest.py
index dae27eba..0ac14028 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -62,7 +62,11 @@ class LocalRepo(pytest.File):
     def collect(self):
         yield Repo2DockerTest(
             self.fspath.basename, self,
-            args=[self.fspath.dirname, './verify'],
+            args=[
+                '--appendix', 'RUN echo "appendix" > /tmp/appendix',
+                self.fspath.dirname,
+                './verify',
+            ],
         )
 
 
diff --git a/tests/venv/default/verify b/tests/venv/default/verify
index f815f7b9..3be5a216 100755
--- a/tests/venv/default/verify
+++ b/tests/venv/default/verify
@@ -2,5 +2,8 @@
 # Verify that the default just provides a py3 environment with jupyter
 import sys
 
-assert sys.version_info[:2] == (3, 6)
+assert sys.version_info[:2] == (3, 6), sys.version
 import jupyter
+
+with open('/tmp/appendix') as f:
+    assert f.read().strip() == 'appendix'