diff --git a/pre_commit/languages/node.py b/pre_commit/languages/node.py
index 839daf00..7f78fdb4 100644
--- a/pre_commit/languages/node.py
+++ b/pre_commit/languages/node.py
@@ -47,11 +47,13 @@ def install_environment(
         with in_env(repo_cmd_runner, version) as node_env:
             node_env.run("cd '{prefix}' && npm install -g")
             if additional_dependencies:
-                node_env.run("cd '{prefix}' && npm install -g {deps}".format(
+                node_env.run(
+                    "cd '{prefix}' && npm install -g " +
                     ' '.join(
-                        [shell_escape(dep) for dep in additional_dependencies]
+                        [shell_escape(dep) for dep in
+                         additional_dependencies]
                     )
-                ))
+                )
 
 
 def run_hook(repo_cmd_runner, hook, file_args):
diff --git a/pre_commit/languages/python.py b/pre_commit/languages/python.py
index 67e330e3..0268a211 100644
--- a/pre_commit/languages/python.py
+++ b/pre_commit/languages/python.py
@@ -63,11 +63,12 @@ def install_environment(
         with in_env(repo_cmd_runner, version) as env:
             env.run("cd '{prefix}' && pip install .")
             if additional_dependencies:
-                env.run("cd '{prefix}' && pip install  {deps}".format(
+                env.run(
+                    "cd '{prefix}' && pip install " +
                     ' '.join(
                         shell_escape(dep) for dep in additional_dependencies
                     )
-                ))
+                )
 
 
 def run_hook(repo_cmd_runner, hook, file_args):
diff --git a/pre_commit/languages/ruby.py b/pre_commit/languages/ruby.py
index 8d80d5b7..6cf5f457 100644
--- a/pre_commit/languages/ruby.py
+++ b/pre_commit/languages/ruby.py
@@ -98,12 +98,12 @@ def install_environment(
             )
             if additional_dependencies:
                 ruby_env.run(
-                    'cd {prefix} && gem install --no-document  {deps}'.format(
-                        ' '.join(
-                            shell_escape(dep) for dep in
-                            additional_dependencies
-                        )
-                    ))
+                    'cd {prefix} && gem install --no-document ' +
+                    ' '.join(
+                        shell_escape(dep) for dep in
+                        additional_dependencies
+                    )
+                )
 
 
 def run_hook(repo_cmd_runner, hook, file_args):
diff --git a/tests/repository_test.py b/tests/repository_test.py
index 798cff67..e02e3653 100644
--- a/tests/repository_test.py
+++ b/tests/repository_test.py
@@ -5,6 +5,7 @@ import io
 import os
 import os.path
 import shutil
+from collections import defaultdict
 
 import mock
 import pytest
@@ -278,6 +279,7 @@ def mock_repo_config():
         'hooks': [{
             'id': 'pyflakes',
             'files': '\\.py$',
+            'additional_dependencies': ['pep8']
         }],
     }
     config_wrapped = apply_defaults([config], CONFIG_JSON_SCHEMA)
@@ -303,6 +305,52 @@ def test_languages(tempdir_factory, store):
     assert repo.languages == set([('python', 'default')])
 
 
+@pytest.mark.integration
+def test_additional_dependencies(tempdir_factory, store):
+    path = make_repo(tempdir_factory, 'python_hooks_repo')
+    config = make_config_from_repo(path)
+    config['hooks'][0]['additional_dependencies'] = ['pep8']
+    repo = Repository.create(config, store)
+    expected_deps = defaultdict(lambda: defaultdict(set))
+    expected_deps['python']['default'].update(['pep8'])
+    assert repo.additional_dependencies == expected_deps
+
+
+@pytest.mark.integration
+def test_additional_python_dependencies_installed(tempdir_factory, store):
+    path = make_repo(tempdir_factory, 'python_hooks_repo')
+    config = make_config_from_repo(path)
+    config['hooks'][0]['additional_dependencies'] = ['pep8']
+    repo = Repository.create(config, store)
+    repo.run_hook(repo.hooks[0][1], [])
+    output = repo.cmd_runner.run(['pip', 'freeze'])
+    assert 'pep8' in output[1]
+
+
+@pytest.mark.integration
+def test_additional_ruby_dependencies_installed(tempdir_factory, store):
+    path = make_repo(tempdir_factory, 'ruby_hooks_repo')
+    config = make_config_from_repo(path)
+    config['hooks'][0]['additional_dependencies'] = ['rubocop']
+    repo = Repository.create(config, store)
+    repo.run_hook(repo.hooks[0][1], [])
+    output = repo.cmd_runner.run(['gem', 'list', '--local'])
+    assert 'rubocop' in output[1]
+
+
+@pytest.mark.integration
+def test_additional_node_dependencies_installed(tempdir_factory, store):
+    path = make_repo(tempdir_factory, 'node_hooks_repo')
+    config = make_config_from_repo(path)
+    config['hooks'][0]['additional_dependencies'] = ['eslint']
+    repo = Repository.create(config, store)
+    repo.run_hook(repo.hooks[0][1], [])
+    repo.cmd_runner.run(['npm', 'config', 'set', 'global', 'true',
+                         '&&', 'npm', 'ls'])
+    output = repo.cmd_runner.run(['npm', 'ls'])
+    assert 'eslint' in output[1]
+
+
 def test_reinstall(tempdir_factory, store, log_info_mock):
     path = make_repo(tempdir_factory, 'python_hooks_repo')
     config = make_config_from_repo(path)