diff --git a/docs/hooks.py b/docs/hooks.py
index 1ab58b88..34b556f1 100644
--- a/docs/hooks.py
+++ b/docs/hooks.py
@@ -16,7 +16,7 @@ def _get_language_of_translation_file(path: Path) -> str:
 
 def on_page_markdown(markdown: str, page: Page, config: MkDocsConfig, **kwargs):
     if page.file.src_uri == 'user-guide/choosing-your-theme.md':
-        here = Path(config.config_file_path or '').parent
+        here = Path(config.config_file_path).parent
 
         def replacement(m: re.Match) -> str:
             lines = []
diff --git a/mkdocs/commands/gh_deploy.py b/mkdocs/commands/gh_deploy.py
index de5fb99b..f6e5fa05 100644
--- a/mkdocs/commands/gh_deploy.py
+++ b/mkdocs/commands/gh_deploy.py
@@ -116,7 +116,7 @@ def gh_deploy(
 
     if message is None:
         message = default_message
-    sha = _get_current_sha(os.path.dirname(config.config_file_path or ''))
+    sha = _get_current_sha(os.path.dirname(config.config_file_path))
     message = message.format(version=mkdocs.__version__, sha=sha)
 
     log.info(
diff --git a/mkdocs/commands/serve.py b/mkdocs/commands/serve.py
index 48095f9b..1797e815 100644
--- a/mkdocs/commands/serve.py
+++ b/mkdocs/commands/serve.py
@@ -100,7 +100,8 @@ def serve(
         if livereload:
             # Watch the documentation files, the config file and the theme files.
             server.watch(config.docs_dir)
-            server.watch(config.config_file_path)
+            if config.config_file_path:
+                server.watch(config.config_file_path)
 
             if watch_theme:
                 for d in config.theme.dirs:
diff --git a/mkdocs/config/base.py b/mkdocs/config/base.py
index dcbc6e23..14f1d953 100644
--- a/mkdocs/config/base.py
+++ b/mkdocs/config/base.py
@@ -133,7 +133,7 @@ class Config(UserDict):
     """
 
     _schema: PlainConfigSchema
-    config_file_path: str | None
+    config_file_path: str
 
     def __init_subclass__(cls):
         schema = dict(getattr(cls, '_schema', ()))
@@ -170,7 +170,7 @@ class Config(UserDict):
                 config_file_path = config_file_path.decode(encoding=sys.getfilesystemencoding())
             except UnicodeDecodeError:
                 raise ValidationError("config_file_path is not a Unicode string.")
-        self.config_file_path = config_file_path
+        self.config_file_path = config_file_path or ''
 
     def set_defaults(self) -> None:
         """
@@ -344,7 +344,9 @@ def _open_config_file(config_file: str | IO | None) -> Iterator[IO]:
             result_config_file.close()
 
 
-def load_config(config_file: str | IO | None = None, **kwargs) -> MkDocsConfig:
+def load_config(
+    config_file: str | IO | None = None, *, config_file_path: str | None = None, **kwargs
+) -> MkDocsConfig:
     """
     Load the configuration for a given file object or name
 
@@ -366,7 +368,10 @@ def load_config(config_file: str | IO | None = None, **kwargs) -> MkDocsConfig:
         # Initialize the config with the default schema.
         from mkdocs.config.defaults import MkDocsConfig
 
-        cfg = MkDocsConfig(config_file_path=getattr(fd, 'name', ''))
+        if config_file_path is None:
+            if fd is not sys.stdin.buffer:
+                config_file_path = getattr(fd, 'name', None)
+        cfg = MkDocsConfig(config_file_path=config_file_path)
         # load the config file
         cfg.load_file(fd)
 
diff --git a/mkdocs/config/config_options.py b/mkdocs/config/config_options.py
index 23a113c0..05994b03 100644
--- a/mkdocs/config/config_options.py
+++ b/mkdocs/config/config_options.py
@@ -708,7 +708,7 @@ class Dir(FilesystemObject):
 
 class DocsDir(Dir):
     def post_validation(self, config: Config, key_name: str):
-        if config.config_file_path is None:
+        if not config.config_file_path:
             return
 
         # Validate that the dir is not the parent dir of the config file.
@@ -826,7 +826,7 @@ class Theme(BaseConfigOption[theme.Theme]):
 
         # Ensure custom_dir is an absolute path
         if 'custom_dir' in theme_config and not os.path.isabs(theme_config['custom_dir']):
-            config_dir = os.path.dirname(self.config_file_path or '')
+            config_dir = os.path.dirname(self.config_file_path)
             theme_config['custom_dir'] = os.path.join(config_dir, theme_config['custom_dir'])
 
         if 'custom_dir' in theme_config and not os.path.isdir(theme_config['custom_dir']):
diff --git a/mkdocs/config/defaults.py b/mkdocs/config/defaults.py
index 891ee710..71e01bcb 100644
--- a/mkdocs/config/defaults.py
+++ b/mkdocs/config/defaults.py
@@ -16,7 +16,7 @@ def get_schema() -> base.PlainConfigSchema:
 class MkDocsConfig(base.Config):
     """The configuration of MkDocs itself (the root object of mkdocs.yml)."""
 
-    config_file_path: str | None = c.Optional(c.Type(str))  # type: ignore[assignment]
+    config_file_path: str = c.Type(str)  # type: ignore[assignment]
     """The path to the mkdocs.yml config file. Can't be populated from the config."""
 
     site_name = c.Type(str)