diff --git a/sphinx/application.py b/sphinx/application.py
index d5fbaa9f3..4e1b4b7ba 100644
--- a/sphinx/application.py
+++ b/sphinx/application.py
@@ -22,7 +22,7 @@ from pygments.lexer import Lexer  # NoQA: TCH002
 
 import sphinx
 from sphinx import locale, package_dir
-from sphinx.config import Config
+from sphinx.config import Config, _ConfigRebuild
 from sphinx.environment import BuildEnvironment
 from sphinx.errors import ApplicationError, ConfigError, VersionRequirementError
 from sphinx.events import EventManager
@@ -507,7 +507,7 @@ class Sphinx:
         self.registry.add_builder(builder, override=override)
 
     # TODO(stephenfin): Describe 'types' parameter
-    def add_config_value(self, name: str, default: Any, rebuild: bool | str,
+    def add_config_value(self, name: str, default: Any, rebuild: _ConfigRebuild,
                          types: Any = ()) -> None:
         """Register a configuration value.
 
diff --git a/sphinx/builders/epub3.py b/sphinx/builders/epub3.py
index 40d3ce7ee..0b438cce7 100644
--- a/sphinx/builders/epub3.py
+++ b/sphinx/builders/epub3.py
@@ -260,7 +260,7 @@ def setup(app: Sphinx) -> dict[str, Any]:
     app.add_builder(Epub3Builder)
 
     # config values
-    app.add_config_value('epub_basename', lambda self: make_filename(self.project), False)
+    app.add_config_value('epub_basename', lambda self: make_filename(self.project), '')
     app.add_config_value('epub_version', 3.0, 'epub')  # experimental
     app.add_config_value('epub_theme', 'epub', 'epub')
     app.add_config_value('epub_theme_options', {}, 'epub')
diff --git a/sphinx/builders/latex/__init__.py b/sphinx/builders/latex/__init__.py
index 52fd6b2c6..16e7fe519 100644
--- a/sphinx/builders/latex/__init__.py
+++ b/sphinx/builders/latex/__init__.py
@@ -526,26 +526,26 @@ def setup(app: Sphinx) -> dict[str, Any]:
     app.connect('config-inited', validate_latex_theme_options, priority=800)
     app.connect('builder-inited', install_packages_for_ja)
 
-    app.add_config_value('latex_engine', default_latex_engine, False,
+    app.add_config_value('latex_engine', default_latex_engine, '',
                          ENUM('pdflatex', 'xelatex', 'lualatex', 'platex', 'uplatex'))
-    app.add_config_value('latex_documents', default_latex_documents, False)
-    app.add_config_value('latex_logo', None, False, [str])
-    app.add_config_value('latex_appendices', [], False)
-    app.add_config_value('latex_use_latex_multicolumn', False, False)
-    app.add_config_value('latex_use_xindy', default_latex_use_xindy, False, [bool])
-    app.add_config_value('latex_toplevel_sectioning', None, False,
+    app.add_config_value('latex_documents', default_latex_documents, '')
+    app.add_config_value('latex_logo', None, '', [str])
+    app.add_config_value('latex_appendices', [], '')
+    app.add_config_value('latex_use_latex_multicolumn', False, '')
+    app.add_config_value('latex_use_xindy', default_latex_use_xindy, '', [bool])
+    app.add_config_value('latex_toplevel_sectioning', None, '',
                          ENUM(None, 'part', 'chapter', 'section'))
-    app.add_config_value('latex_domain_indices', True, False, [list])
-    app.add_config_value('latex_show_urls', 'no', False)
-    app.add_config_value('latex_show_pagerefs', False, False)
-    app.add_config_value('latex_elements', {}, False)
-    app.add_config_value('latex_additional_files', [], False)
-    app.add_config_value('latex_table_style', ['booktabs', 'colorrows'], False, [list])
-    app.add_config_value('latex_theme', 'manual', False, [str])
-    app.add_config_value('latex_theme_options', {}, False)
-    app.add_config_value('latex_theme_path', [], False, [list])
+    app.add_config_value('latex_domain_indices', True, '', [list])
+    app.add_config_value('latex_show_urls', 'no', '')
+    app.add_config_value('latex_show_pagerefs', False, '')
+    app.add_config_value('latex_elements', {}, '')
+    app.add_config_value('latex_additional_files', [], '')
+    app.add_config_value('latex_table_style', ['booktabs', 'colorrows'], '', [list])
+    app.add_config_value('latex_theme', 'manual', '', [str])
+    app.add_config_value('latex_theme_options', {}, '')
+    app.add_config_value('latex_theme_path', [], '', [list])
 
-    app.add_config_value('latex_docclass', default_latex_docclass, False)
+    app.add_config_value('latex_docclass', default_latex_docclass, '')
 
     return {
         'version': 'builtin',
diff --git a/sphinx/builders/linkcheck.py b/sphinx/builders/linkcheck.py
index f2509582b..460598ef2 100644
--- a/sphinx/builders/linkcheck.py
+++ b/sphinx/builders/linkcheck.py
@@ -611,20 +611,20 @@ def setup(app: Sphinx) -> dict[str, Any]:
     app.add_builder(CheckExternalLinksBuilder)
     app.add_post_transform(HyperlinkCollector)
 
-    app.add_config_value('linkcheck_ignore', [], False)
-    app.add_config_value('linkcheck_exclude_documents', [], False)
-    app.add_config_value('linkcheck_allowed_redirects', {}, False)
-    app.add_config_value('linkcheck_auth', [], False)
-    app.add_config_value('linkcheck_request_headers', {}, False)
-    app.add_config_value('linkcheck_retries', 1, False)
-    app.add_config_value('linkcheck_timeout', None, False, [int, float])
-    app.add_config_value('linkcheck_workers', 5, False)
-    app.add_config_value('linkcheck_anchors', True, False)
+    app.add_config_value('linkcheck_ignore', [], '')
+    app.add_config_value('linkcheck_exclude_documents', [], '')
+    app.add_config_value('linkcheck_allowed_redirects', {}, '')
+    app.add_config_value('linkcheck_auth', [], '')
+    app.add_config_value('linkcheck_request_headers', {}, '')
+    app.add_config_value('linkcheck_retries', 1, '')
+    app.add_config_value('linkcheck_timeout', None, '', (int, float))
+    app.add_config_value('linkcheck_workers', 5, '')
+    app.add_config_value('linkcheck_anchors', True, '')
     # Anchors starting with ! are ignored since they are
     # commonly used for dynamic pages
-    app.add_config_value('linkcheck_anchors_ignore', ['^!'], False)
-    app.add_config_value('linkcheck_anchors_ignore_for_url', (), False, (tuple, list))
-    app.add_config_value('linkcheck_rate_limit_timeout', 300.0, False)
+    app.add_config_value('linkcheck_anchors_ignore', ['^!'], '')
+    app.add_config_value('linkcheck_anchors_ignore_for_url', (), '', (tuple, list))
+    app.add_config_value('linkcheck_rate_limit_timeout', 300.0, '')
 
     app.add_event('linkcheck-process-uri')
 
diff --git a/sphinx/builders/manpage.py b/sphinx/builders/manpage.py
index 2d35d2047..a5ef29794 100644
--- a/sphinx/builders/manpage.py
+++ b/sphinx/builders/manpage.py
@@ -116,9 +116,9 @@ def default_man_pages(config: Config) -> list[tuple[str, str, str, list[str], in
 def setup(app: Sphinx) -> dict[str, Any]:
     app.add_builder(ManualPageBuilder)
 
-    app.add_config_value('man_pages', default_man_pages, False)
-    app.add_config_value('man_show_urls', False, False)
-    app.add_config_value('man_make_section_directory', False, False)
+    app.add_config_value('man_pages', default_man_pages, '')
+    app.add_config_value('man_show_urls', False, '')
+    app.add_config_value('man_make_section_directory', False, '')
 
     return {
         'version': 'builtin',
diff --git a/sphinx/builders/texinfo.py b/sphinx/builders/texinfo.py
index 441b598ba..cd3a80777 100644
--- a/sphinx/builders/texinfo.py
+++ b/sphinx/builders/texinfo.py
@@ -214,13 +214,13 @@ def default_texinfo_documents(
 def setup(app: Sphinx) -> dict[str, Any]:
     app.add_builder(TexinfoBuilder)
 
-    app.add_config_value('texinfo_documents', default_texinfo_documents, False)
-    app.add_config_value('texinfo_appendices', [], False)
-    app.add_config_value('texinfo_elements', {}, False)
-    app.add_config_value('texinfo_domain_indices', True, False, [list])
-    app.add_config_value('texinfo_show_urls', 'footnote', False)
-    app.add_config_value('texinfo_no_detailmenu', False, False)
-    app.add_config_value('texinfo_cross_references', True, False)
+    app.add_config_value('texinfo_documents', default_texinfo_documents, '')
+    app.add_config_value('texinfo_appendices', [], '')
+    app.add_config_value('texinfo_elements', {}, '')
+    app.add_config_value('texinfo_domain_indices', True, '', [list])
+    app.add_config_value('texinfo_show_urls', 'footnote', '')
+    app.add_config_value('texinfo_no_detailmenu', False, '')
+    app.add_config_value('texinfo_cross_references', True, '')
 
     return {
         'version': 'builtin',
diff --git a/sphinx/config.py b/sphinx/config.py
index e831605c4..f6a5ba1b2 100644
--- a/sphinx/config.py
+++ b/sphinx/config.py
@@ -7,7 +7,7 @@ import time
 import traceback
 import types
 from os import getenv, path
-from typing import TYPE_CHECKING, Any, Callable, NamedTuple
+from typing import TYPE_CHECKING, Any, Callable, Literal, NamedTuple
 
 from sphinx.errors import ConfigError, ExtensionError
 from sphinx.locale import _, __
@@ -30,6 +30,8 @@ if TYPE_CHECKING:
 
 logger = logging.getLogger(__name__)
 
+_ConfigRebuild = Literal['', 'env', 'epub', 'gettext', 'html']
+
 CONFIG_FILENAME = 'conf.py'
 UNSERIALIZABLE_TYPES = (type, types.ModuleType, types.FunctionType)
 
@@ -37,7 +39,7 @@ UNSERIALIZABLE_TYPES = (type, types.ModuleType, types.FunctionType)
 class ConfigValue(NamedTuple):
     name: str
     value: Any
-    rebuild: bool | str
+    rebuild: _ConfigRebuild
 
 
 def is_serializable(obj: Any) -> bool:
@@ -89,7 +91,7 @@ class Config:
 
     # If you add a value here, remember to include it in the docs!
 
-    config_values: dict[str, tuple] = {
+    config_values: dict[str, tuple[Any, _ConfigRebuild, Sequence[type] | ENUM | Any]] = {
         # general options
         'project': ('Python', 'env', []),
         'author': ('unknown', 'env', []),
@@ -134,12 +136,12 @@ class Config:
         'rst_prolog': (None, 'env', [str]),
         'trim_doctest_flags': (True, 'env', []),
         'primary_domain': ('py', 'env', [NoneType]),
-        'needs_sphinx': (None, None, [str]),
-        'needs_extensions': ({}, None, []),
+        'needs_sphinx': (None, '', [str]),
+        'needs_extensions': ({}, '', []),
         'manpages_url': (None, 'env', []),
-        'nitpicky': (False, None, []),
-        'nitpick_ignore': ([], None, [set, list, tuple]),
-        'nitpick_ignore_regex': ([], None, [set, list, tuple]),
+        'nitpicky': (False, '', []),
+        'nitpick_ignore': ([], '', [set, list, tuple]),
+        'nitpick_ignore_regex': ([], '', [set, list, tuple]),
         'numfig': (False, 'env', []),
         'numfig_secnum_depth': (1, 'env', []),
         'numfig_format': ({}, 'env', []),  # will be initialized in init_numfig_format()
@@ -321,7 +323,8 @@ class Config:
         for name, (_default, rebuild, _valid_types) in self.values.items():
             yield ConfigValue(name, getattr(self, name), rebuild)
 
-    def add(self, name: str, default: Any, rebuild: bool | str, types: Any) -> None:
+    def add(self, name: str, default: Any, rebuild: _ConfigRebuild,
+            types: Sequence[type] | ENUM | Any) -> None:
         valid_types = types
         if name in self.values:
             raise ExtensionError(__('Config value %r already present') % name)
diff --git a/sphinx/ext/autodoc/__init__.py b/sphinx/ext/autodoc/__init__.py
index 3f1ed98ae..14292d10f 100644
--- a/sphinx/ext/autodoc/__init__.py
+++ b/sphinx/ext/autodoc/__init__.py
@@ -2821,22 +2821,22 @@ def setup(app: Sphinx) -> dict[str, Any]:
     app.add_autodocumenter(AttributeDocumenter)
     app.add_autodocumenter(PropertyDocumenter)
 
-    app.add_config_value('autoclass_content', 'class', True, ENUM('both', 'class', 'init'))
-    app.add_config_value('autodoc_member_order', 'alphabetical', True,
+    app.add_config_value('autoclass_content', 'class', 'env', ENUM('both', 'class', 'init'))
+    app.add_config_value('autodoc_member_order', 'alphabetical', 'env',
                          ENUM('alphabetical', 'bysource', 'groupwise'))
-    app.add_config_value('autodoc_class_signature', 'mixed', True, ENUM('mixed', 'separated'))
-    app.add_config_value('autodoc_default_options', {}, True)
-    app.add_config_value('autodoc_docstring_signature', True, True)
-    app.add_config_value('autodoc_mock_imports', [], True)
-    app.add_config_value('autodoc_typehints', "signature", True,
+    app.add_config_value('autodoc_class_signature', 'mixed', 'env', ENUM('mixed', 'separated'))
+    app.add_config_value('autodoc_default_options', {}, 'env')
+    app.add_config_value('autodoc_docstring_signature', True, 'env')
+    app.add_config_value('autodoc_mock_imports', [], 'env')
+    app.add_config_value('autodoc_typehints', "signature", 'env',
                          ENUM("signature", "description", "none", "both"))
-    app.add_config_value('autodoc_typehints_description_target', 'all', True,
+    app.add_config_value('autodoc_typehints_description_target', 'all', 'env',
                          ENUM('all', 'documented', 'documented_params'))
-    app.add_config_value('autodoc_type_aliases', {}, True)
+    app.add_config_value('autodoc_type_aliases', {}, 'env')
     app.add_config_value('autodoc_typehints_format', "short", 'env',
                          ENUM("fully-qualified", "short"))
-    app.add_config_value('autodoc_warningiserror', True, True)
-    app.add_config_value('autodoc_inherit_docstrings', True, True)
+    app.add_config_value('autodoc_warningiserror', True, 'env')
+    app.add_config_value('autodoc_inherit_docstrings', True, 'env')
     app.add_event('autodoc-before-process-signature')
     app.add_event('autodoc-process-docstring')
     app.add_event('autodoc-process-signature')
diff --git a/sphinx/ext/autodoc/preserve_defaults.py b/sphinx/ext/autodoc/preserve_defaults.py
index 5f957ce21..5305c6ac9 100644
--- a/sphinx/ext/autodoc/preserve_defaults.py
+++ b/sphinx/ext/autodoc/preserve_defaults.py
@@ -190,7 +190,7 @@ def update_defvalue(app: Sphinx, obj: Any, bound_method: bool) -> None:
 
 
 def setup(app: Sphinx) -> dict[str, Any]:
-    app.add_config_value('autodoc_preserve_defaults', False, True)
+    app.add_config_value('autodoc_preserve_defaults', False, 'env')
     app.connect('autodoc-before-process-signature', update_defvalue)
 
     return {
diff --git a/sphinx/ext/autosummary/__init__.py b/sphinx/ext/autosummary/__init__.py
index edb8f0d5f..a13b38790 100644
--- a/sphinx/ext/autosummary/__init__.py
+++ b/sphinx/ext/autosummary/__init__.py
@@ -162,7 +162,7 @@ class FakeDirective(DocumenterBridge):
         settings = Struct(tab_width=8)
         document = Struct(settings=settings)
         app = FakeApplication()
-        app.config.add('autodoc_class_signature', 'mixed', True, None)
+        app.config.add('autodoc_class_signature', 'mixed', 'env', None)
         env = BuildEnvironment(app)  # type: ignore[arg-type]
         state = Struct(document=document)
         super().__init__(env, None, Options(), 0, state)
@@ -835,13 +835,13 @@ def setup(app: Sphinx) -> dict[str, Any]:
     app.add_directive('autosummary', Autosummary)
     app.add_role('autolink', AutoLink())
     app.connect('builder-inited', process_generate_options)
-    app.add_config_value('autosummary_context', {}, True)
+    app.add_config_value('autosummary_context', {}, 'env')
     app.add_config_value('autosummary_filename_map', {}, 'html')
-    app.add_config_value('autosummary_generate', True, True, [bool, list])
-    app.add_config_value('autosummary_generate_overwrite', True, False)
+    app.add_config_value('autosummary_generate', True, 'env', [bool, list])
+    app.add_config_value('autosummary_generate_overwrite', True, '')
     app.add_config_value('autosummary_mock_imports',
                          lambda config: config.autodoc_mock_imports, 'env')
-    app.add_config_value('autosummary_imported_members', [], False, [bool])
+    app.add_config_value('autosummary_imported_members', [], '', [bool])
     app.add_config_value('autosummary_ignore_module_all', True, 'env', bool)
 
     return {'version': sphinx.__display_version__, 'parallel_read_safe': True}
diff --git a/sphinx/ext/autosummary/generate.py b/sphinx/ext/autosummary/generate.py
index 06814f9ba..c78c15be6 100644
--- a/sphinx/ext/autosummary/generate.py
+++ b/sphinx/ext/autosummary/generate.py
@@ -71,8 +71,8 @@ class DummyApplication:
         self._warncount = 0
         self.warningiserror = False
 
-        self.config.add('autosummary_context', {}, True, None)
-        self.config.add('autosummary_filename_map', {}, True, None)
+        self.config.add('autosummary_context', {}, 'env', None)
+        self.config.add('autosummary_filename_map', {}, 'env', None)
         self.config.add('autosummary_ignore_module_all', True, 'env', bool)
         self.config.init_values()
 
diff --git a/sphinx/ext/coverage.py b/sphinx/ext/coverage.py
index 02096afbc..3cf57ef62 100644
--- a/sphinx/ext/coverage.py
+++ b/sphinx/ext/coverage.py
@@ -389,16 +389,16 @@ class CoverageBuilder(Builder):
 
 def setup(app: Sphinx) -> dict[str, Any]:
     app.add_builder(CoverageBuilder)
-    app.add_config_value('coverage_ignore_modules', [], False)
-    app.add_config_value('coverage_ignore_functions', [], False)
-    app.add_config_value('coverage_ignore_classes', [], False)
-    app.add_config_value('coverage_ignore_pyobjects', [], False)
-    app.add_config_value('coverage_c_path', [], False)
-    app.add_config_value('coverage_c_regexes', {}, False)
-    app.add_config_value('coverage_ignore_c_items', {}, False)
-    app.add_config_value('coverage_write_headline', True, False)
-    app.add_config_value('coverage_statistics_to_report', True, False, (bool,))
-    app.add_config_value('coverage_statistics_to_stdout', True, False, (bool,))
-    app.add_config_value('coverage_skip_undoc_in_source', False, False)
-    app.add_config_value('coverage_show_missing_items', False, False)
+    app.add_config_value('coverage_ignore_modules', [], '')
+    app.add_config_value('coverage_ignore_functions', [], '')
+    app.add_config_value('coverage_ignore_classes', [], '')
+    app.add_config_value('coverage_ignore_pyobjects', [], '')
+    app.add_config_value('coverage_c_path', [], '')
+    app.add_config_value('coverage_c_regexes', {}, '')
+    app.add_config_value('coverage_ignore_c_items', {}, '')
+    app.add_config_value('coverage_write_headline', True, '')
+    app.add_config_value('coverage_statistics_to_report', True, '', (bool,))
+    app.add_config_value('coverage_statistics_to_stdout', True, '', (bool,))
+    app.add_config_value('coverage_skip_undoc_in_source', False, '')
+    app.add_config_value('coverage_show_missing_items', False, '')
     return {'version': sphinx.__display_version__, 'parallel_read_safe': True}
diff --git a/sphinx/ext/doctest.py b/sphinx/ext/doctest.py
index c55ef2fa7..ef93df42d 100644
--- a/sphinx/ext/doctest.py
+++ b/sphinx/ext/doctest.py
@@ -563,13 +563,13 @@ def setup(app: Sphinx) -> dict[str, Any]:
     app.add_directive('testoutput', TestoutputDirective)
     app.add_builder(DocTestBuilder)
     # this config value adds to sys.path
-    app.add_config_value('doctest_show_successes', True, False, (bool,))
-    app.add_config_value('doctest_path', [], False)
-    app.add_config_value('doctest_test_doctest_blocks', 'default', False)
-    app.add_config_value('doctest_global_setup', '', False)
-    app.add_config_value('doctest_global_cleanup', '', False)
+    app.add_config_value('doctest_show_successes', True, '', (bool,))
+    app.add_config_value('doctest_path', [], '')
+    app.add_config_value('doctest_test_doctest_blocks', 'default', '')
+    app.add_config_value('doctest_global_setup', '', '')
+    app.add_config_value('doctest_global_cleanup', '', '')
     app.add_config_value(
         'doctest_default_flags',
         doctest.DONT_ACCEPT_TRUE_FOR_1 | doctest.ELLIPSIS | doctest.IGNORE_EXCEPTION_DETAIL,
-        False)
+        '')
     return {'version': sphinx.__display_version__, 'parallel_read_safe': True}
diff --git a/sphinx/ext/inheritance_diagram.py b/sphinx/ext/inheritance_diagram.py
index 3a015a2b1..f737d05cf 100644
--- a/sphinx/ext/inheritance_diagram.py
+++ b/sphinx/ext/inheritance_diagram.py
@@ -487,8 +487,8 @@ def setup(app: Sphinx) -> dict[str, Any]:
         man=(skip, None),
         texinfo=(texinfo_visit_inheritance_diagram, None))
     app.add_directive('inheritance-diagram', InheritanceDiagram)
-    app.add_config_value('inheritance_graph_attrs', {}, False)
-    app.add_config_value('inheritance_node_attrs', {}, False)
-    app.add_config_value('inheritance_edge_attrs', {}, False)
-    app.add_config_value('inheritance_alias', {}, False)
+    app.add_config_value('inheritance_graph_attrs', {}, '')
+    app.add_config_value('inheritance_node_attrs', {}, '')
+    app.add_config_value('inheritance_edge_attrs', {}, '')
+    app.add_config_value('inheritance_alias', {}, '')
     return {'version': sphinx.__display_version__, 'parallel_read_safe': True}
diff --git a/sphinx/ext/intersphinx.py b/sphinx/ext/intersphinx.py
index 453bb6e98..d2b14bf04 100644
--- a/sphinx/ext/intersphinx.py
+++ b/sphinx/ext/intersphinx.py
@@ -682,10 +682,10 @@ def normalize_intersphinx_mapping(app: Sphinx, config: Config) -> None:
 
 
 def setup(app: Sphinx) -> dict[str, Any]:
-    app.add_config_value('intersphinx_mapping', {}, True)
-    app.add_config_value('intersphinx_cache_limit', 5, False)
-    app.add_config_value('intersphinx_timeout', None, False)
-    app.add_config_value('intersphinx_disabled_reftypes', ['std:doc'], True)
+    app.add_config_value('intersphinx_mapping', {}, 'env')
+    app.add_config_value('intersphinx_cache_limit', 5, '')
+    app.add_config_value('intersphinx_timeout', None, '')
+    app.add_config_value('intersphinx_disabled_reftypes', ['std:doc'], 'env')
     app.connect('config-inited', normalize_intersphinx_mapping, priority=800)
     app.connect('builder-inited', load_mappings)
     app.connect('source-read', install_dispatcher)
diff --git a/sphinx/ext/napoleon/__init__.py b/sphinx/ext/napoleon/__init__.py
index 61aa3d83f..fd98ffbcd 100644
--- a/sphinx/ext/napoleon/__init__.py
+++ b/sphinx/ext/napoleon/__init__.py
@@ -2,13 +2,16 @@
 
 from __future__ import annotations
 
-from typing import Any
+from typing import TYPE_CHECKING, Any
 
 import sphinx
 from sphinx.application import Sphinx
 from sphinx.ext.napoleon.docstring import GoogleDocstring, NumpyDocstring
 from sphinx.util import inspect
 
+if TYPE_CHECKING:
+    from sphinx.config import _ConfigRebuild
+
 
 class Config:
     """Sphinx napoleon extension settings in `conf.py`.
@@ -262,7 +265,7 @@ class Config:
         but do not have a type in the docstring.
 
     """
-    _config_values = {
+    _config_values: dict[str, tuple[Any, _ConfigRebuild]] = {
         'napoleon_google_docstring': (True, 'env'),
         'napoleon_numpy_docstring': (True, 'env'),
         'napoleon_include_init_with_doc': (False, 'env'),
diff --git a/sphinx/ext/viewcode.py b/sphinx/ext/viewcode.py
index c5fcda537..e8794aec0 100644
--- a/sphinx/ext/viewcode.py
+++ b/sphinx/ext/viewcode.py
@@ -341,9 +341,9 @@ def collect_pages(app: Sphinx) -> Generator[tuple[str, dict[str, Any], str], Non
 
 
 def setup(app: Sphinx) -> dict[str, Any]:
-    app.add_config_value('viewcode_import', None, False)
-    app.add_config_value('viewcode_enable_epub', False, False)
-    app.add_config_value('viewcode_follow_imported_members', True, False)
+    app.add_config_value('viewcode_import', None, '')
+    app.add_config_value('viewcode_enable_epub', False, '')
+    app.add_config_value('viewcode_follow_imported_members', True, '')
     app.add_config_value('viewcode_line_numbers', False, 'env', (bool,))
     app.connect('doctree-read', doctree_read)
     app.connect('env-merge-info', env_merge_info)