diff --git a/CHANGES/9972.bugfix.rst b/CHANGES/9972.bugfix.rst
new file mode 100644
index 00000000000..d8d69d09044
--- /dev/null
+++ b/CHANGES/9972.bugfix.rst
@@ -0,0 +1,3 @@
+Reverted an optimization to avoid rebuilding the allowed methods for ``StaticResource`` on every request -- by :user:`bdraco`.
+
+``aiohttp-cors`` needs to be able to modify the allowed methods at run time via this internal.
diff --git a/aiohttp/web_urldispatcher.py b/aiohttp/web_urldispatcher.py
index e4d43514ebe..025962bc594 100644
--- a/aiohttp/web_urldispatcher.py
+++ b/aiohttp/web_urldispatcher.py
@@ -580,7 +580,6 @@ def __init__(
                 "HEAD", self._handle, self, expect_handler=expect_handler
             ),
         }
-        self._allowed_methods = set(self._routes)
 
     def url_for(  # type: ignore[override]
         self,
@@ -650,7 +649,7 @@ async def resolve(self, request: Request) -> _Resolve:
         if not path.startswith(self._prefix2) and path != self._prefix:
             return None, set()
 
-        allowed_methods = self._allowed_methods
+        allowed_methods = set(self._routes)
         if method not in allowed_methods:
             return None, allowed_methods