diff --git a/mypy/metastore.py b/mypy/metastore.py
index c9139045e3b1..21fb8730f2c9 100644
--- a/mypy/metastore.py
+++ b/mypy/metastore.py
@@ -131,7 +131,7 @@ def list_all(self) -> Iterable[str]:
         for dir, _, files in os.walk(self.cache_dir_prefix):
             dir = os.path.relpath(dir, self.cache_dir_prefix)
             for file in files:
-                yield os.path.join(dir, file)
+                yield os.path.normpath(os.path.join(dir, file))
 
 
 SCHEMA = """