diff --git a/mercurial/osutil.py b/mercurial/osutil.py
--- a/mercurial/osutil.py
+++ b/mercurial/osutil.py
@@ -26,7 +26,9 @@ def listdir(path, stat=False, skip=None)
       (name, type)
     '''
     result = []
-    prefix = path + os.sep
+    prefix = path
+    if not prefix.endswith(os.sep):
+        prefix += os.sep
     names = os.listdir(path)
     names.sort()
     for fn in names:
diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -856,7 +856,7 @@ def _statfiles_clustered(files):
         if pos == -1:
             dir, base = '.', nf
         else:
-            dir, base = nf[:pos], nf[pos+1:]
+            dir, base = nf[:pos+1], nf[pos+1:]
         cache = dircache.get(dir, None)
         if cache is None:
             try: