diff --git a/src/libtmux/_internal/types.py b/src/libtmux/_internal/types.py
new file mode 100644
index 000000000..7e9953dfe
--- /dev/null
+++ b/src/libtmux/_internal/types.py
@@ -0,0 +1,19 @@
+"""Internal type annotations.
+
+Notes
+-----
+:class:`StrPath` and :class:`StrOrBytesPath` is based on `typeshed's`_.
+
+.. _typeshed's: https://github.com/python/typeshed/blob/5ff32f3/stdlib/_typeshed/__init__.pyi#L176-L179
+"""  # E501
+
+from __future__ import annotations
+
+import typing as t
+
+if t.TYPE_CHECKING:
+    from os import PathLike
+
+    from typing_extensions import TypeAlias
+
+StrPath: TypeAlias = "str | PathLike[str]"
diff --git a/src/libtmux/session.py b/src/libtmux/session.py
index 1b8af4563..1016d423c 100644
--- a/src/libtmux/session.py
+++ b/src/libtmux/session.py
@@ -34,6 +34,7 @@
     import sys
     import types
 
+    from libtmux._internal.types import StrPath
     from libtmux.common import tmux_cmd
 
     if sys.version_info >= (3, 11):
@@ -587,7 +588,7 @@ def new_window(
         self,
         window_name: str | None = None,
         *,
-        start_directory: str | None = None,
+        start_directory: StrPath | None = None,
         attach: bool = False,
         window_index: str = "",
         window_shell: str | None = None,
@@ -677,7 +678,8 @@ def new_window(
 
         window_args += ("-P",)
 
-        if start_directory is not None:
+        # Catch empty string and default (`None`)
+        if start_directory and isinstance(start_directory, str):
             # as of 2014-02-08 tmux 1.9-dev doesn't expand ~ in new-window -c.
             start_directory = pathlib.Path(start_directory).expanduser()
             window_args += (f"-c{start_directory}",)