diff --git a/importlib_resources/future/adapters.py b/importlib_resources/future/adapters.py
index 9aa5b5e..9d26bf4 100644
--- a/importlib_resources/future/adapters.py
+++ b/importlib_resources/future/adapters.py
@@ -24,7 +24,8 @@ def wrapper(*args, **kwargs):
             # MultiplexedPath may fail on zip subdirectory
             return
         # Python 3.10+
-        if reader.__class__.__module__.startswith('importlib.resources.'):
+        mod_name = reader.__class__.__module__
+        if mod_name.startswith('importlib.') and mod_name.endswith('readers'):
             return
         # Python 3.8, 3.9
         if isinstance(reader, _adapters.CompatibilityFiles) and (
diff --git a/importlib_resources/tests/test_files.py b/importlib_resources/tests/test_files.py
index 9e45f70..3e86ec6 100644
--- a/importlib_resources/tests/test_files.py
+++ b/importlib_resources/tests/test_files.py
@@ -34,6 +34,11 @@ def test_read_text(self):
     def test_traversable(self):
         assert isinstance(resources.files(self.data), Traversable)
 
+    def test_joinpath_with_multiple_args(self):
+        files = resources.files(self.data)
+        binfile = files.joinpath('subdirectory', 'binary.file')
+        self.assertTrue(binfile.is_file())
+
     def test_old_parameter(self):
         """
         Files used to take a 'package' parameter. Make sure anyone
diff --git a/newsfragments/257.bugfix.rst b/newsfragments/257.bugfix.rst
new file mode 100644
index 0000000..d8feffd
--- /dev/null
+++ b/newsfragments/257.bugfix.rst
@@ -0,0 +1 @@
+Restored expectation that stdlib readers are suppressed on Python 3.10.
\ No newline at end of file