diff --git a/tests/check_consistent.py b/tests/check_consistent.py
@@ -23,7 +23,9 @@
 supported_stubtest_platforms = {"win32", "darwin", "linux"}
 
 
-def assert_consistent_filetypes(directory: Path, *, kind: str, allowed: set[str]) -> None:
+def assert_consistent_filetypes(
+    directory: Path, *, kind: str, allowed: set[str], allow_nonidentifier_filenames: bool = False
+) -> None:
     """Check that given directory contains only valid Python files of a certain kind."""
     allowed_paths = {Path(f) for f in allowed}
     contents = list(directory.iterdir())
@@ -36,8 +38,9 @@ def assert_consistent_filetypes(directory: Path, *, kind: str, allowed: set[str]
             # Note if a subdirectory is allowed, we will not check its contents
             continue
         if entry.is_file():
-            assert entry.stem.isidentifier(), f'Files must be valid modules, got: "{entry}"'
-            bad_filetype = f'Only {extension_descriptions[kind]!r} files allowed in the "{directory}" directory; got: {entry}'
+            if not allow_nonidentifier_filenames:
+                assert entry.stem.isidentifier(), f'Files must be valid modules, got: "{entry}"'
+                bad_filetype = f'Only {extension_descriptions[kind]!r} files allowed in the "{directory}" directory; got: {entry}'
             assert entry.suffix == kind, bad_filetype
         else:
             assert entry.name.isidentifier(), f"Directories must be valid packages, got: {entry}"
@@ -67,7 +70,7 @@ def check_stubs() -> None:
 
 def check_test_cases() -> None:
     for package_name, testcase_dir in get_all_testcase_directories():
-        assert_consistent_filetypes(testcase_dir, kind=".py", allowed={"README.md"})
+        assert_consistent_filetypes(testcase_dir, kind=".py", allowed={"README.md"}, allow_nonidentifier_filenames=True)
         bad_test_case_filename = 'Files in a `test_cases` directory must have names starting with "check_"; got "{}"'
         for file in testcase_dir.rglob("*.py"):
             assert file.stem.startswith("check_"), bad_test_case_filename.format(file)