diff --git a/readthedocs/doc_builder/base.py b/readthedocs/doc_builder/base.py
index df9882c56f0..83aac0da617 100644
--- a/readthedocs/doc_builder/base.py
+++ b/readthedocs/doc_builder/base.py
@@ -46,7 +46,7 @@ def __init__(self, build_env, python_env, force=False):
         self.python_env = python_env
         self.version = build_env.version
         self.project = build_env.project
-        self.config = python_env.config
+        self.config = python_env.config if python_env else None
         self._force = force
         self.target = self.project.artifact_path(
             version=self.version.slug, type_=self.type)
diff --git a/readthedocs/rtd_tests/tests/test_doc_builder.py b/readthedocs/rtd_tests/tests/test_doc_builder.py
index 3de7192b4a7..b07668f1084 100644
--- a/readthedocs/rtd_tests/tests/test_doc_builder.py
+++ b/readthedocs/rtd_tests/tests/test_doc_builder.py
@@ -292,81 +292,6 @@ def test_append_conf_existing_yaml_on_root(self, checkout_path, run):
             'mkdocs'
         )
 
-    @patch('readthedocs.doc_builder.base.BaseBuilder.run')
-    @patch('readthedocs.projects.models.Project.checkout_path')
-    def test_override_theme_new_style(self, checkout_path, run):
-        tmpdir = tempfile.mkdtemp()
-        os.mkdir(os.path.join(tmpdir, 'docs'))
-        yaml_file = os.path.join(tmpdir, 'mkdocs.yml')
-        yaml.safe_dump(
-            {
-                'theme': {
-                    'name': 'readthedocs',
-                },
-                'site_name': 'mkdocs',
-                'docs_dir': 'docs',
-            },
-            open(yaml_file, 'w')
-        )
-        checkout_path.return_value = tmpdir
-
-        python_env = Virtualenv(
-            version=self.version,
-            build_env=self.build_env,
-            config=None,
-        )
-        self.searchbuilder = MkdocsHTML(
-            build_env=self.build_env,
-            python_env=python_env,
-        )
-        self.searchbuilder.append_conf()
-
-        run.assert_called_with('cat', 'mkdocs.yml', cwd=mock.ANY)
-
-        config = yaml.safe_load(open(yaml_file))
-        self.assertEqual(
-            config['theme'],
-            {
-                'name': 'readthedocs',
-                'custom_dir': BaseMkdocs.READTHEDOCS_TEMPLATE_OVERRIDE_DIR
-            }
-        )
-
-    @patch('readthedocs.doc_builder.base.BaseBuilder.run')
-    @patch('readthedocs.projects.models.Project.checkout_path')
-    def test_override_theme_old_style(self, checkout_path, run):
-        tmpdir = tempfile.mkdtemp()
-        os.mkdir(os.path.join(tmpdir, 'docs'))
-        yaml_file = os.path.join(tmpdir, 'mkdocs.yml')
-        yaml.safe_dump(
-            {
-                'theme': 'readthedocs',
-                'site_name': 'mkdocs',
-                'docs_dir': 'docs',
-            },
-            open(yaml_file, 'w')
-        )
-        checkout_path.return_value = tmpdir
-
-        python_env = Virtualenv(
-            version=self.version,
-            build_env=self.build_env,
-            config=None,
-        )
-        self.searchbuilder = MkdocsHTML(
-            build_env=self.build_env,
-            python_env=python_env,
-        )
-        self.searchbuilder.append_conf()
-
-        run.assert_called_with('cat', 'mkdocs.yml', cwd=mock.ANY)
-
-        config = yaml.safe_load(open(yaml_file))
-        self.assertEqual(
-            config['theme_dir'],
-            BaseMkdocs.READTHEDOCS_TEMPLATE_OVERRIDE_DIR
-        )
-
     @patch('readthedocs.doc_builder.base.BaseBuilder.run')
     @patch('readthedocs.projects.models.Project.checkout_path')
     def test_dont_override_theme(self, checkout_path, run):