diff --git a/git_refs.py b/git_refs.py
index 7feaffb..e0a85d7 100644
--- a/git_refs.py
+++ b/git_refs.py
@@ -15,6 +15,7 @@
 
 import os
 from trace import Trace
+import platform_utils
 
 HEAD      = 'HEAD'
 R_CHANGES = 'refs/changes/'
@@ -127,9 +128,9 @@
 
   def _ReadLoose(self, prefix):
     base = os.path.join(self._gitdir, prefix)
-    for name in os.listdir(base):
+    for name in platform_utils.listdir(base):
       p = os.path.join(base, name)
-      if os.path.isdir(p):
+      if platform_utils.isdir(p):
         self._mtime[prefix] = os.path.getmtime(base)
         self._ReadLoose(prefix + name + '/')
       elif name.endswith('.lock'):