diff --git a/hgext/largefiles/lfutil.py b/hgext/largefiles/lfutil.py
--- a/hgext/largefiles/lfutil.py
+++ b/hgext/largefiles/lfutil.py
@@ -80,7 +80,7 @@
                         encoding.environ.get('APPDATA'))
         if appdata:
             return os.path.join(appdata, longname)
-    elif platform.system() == 'Darwin':
+    elif pycompat.sysplatform == 'darwin':
         home = encoding.environ.get('HOME')
         if home:
             return os.path.join(home, 'Library', 'Caches', longname)