From 6f0c8f75ac164d5d2cc02bba2d63560857f09d68 Mon Sep 17 00:00:00 2001
From: Adam Turner <9087854+aa-turner@users.noreply.github.com>
Date: Mon, 4 Nov 2024 17:28:30 +0000
Subject: [PATCH] Improve lookup in ``Project.path2doc()``

---
 sphinx/project.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sphinx/project.py b/sphinx/project.py
index 016429993..744990860 100644
--- a/sphinx/project.py
+++ b/sphinx/project.py
@@ -96,10 +96,10 @@ class Project:
 
         *filename* should be absolute or relative to the source directory.
         """
+        path = Path(filename)
         try:
-            return self._path_to_docname[filename]  # type: ignore[index]
+            return self._path_to_docname[path]
         except KeyError:
-            path = Path(filename)
             if path.is_absolute():
                 with contextlib.suppress(ValueError):
                     path = path.relative_to(self.srcdir)