diff --git a/hgext/win32mbcs.py b/hgext/win32mbcs.py
--- a/hgext/win32mbcs.py
+++ b/hgext/win32mbcs.py
@@ -128,8 +128,6 @@ def wrapname(name, wrapper):
 #       they use result of os.path.split()
 funcs = '''os.path.join os.path.split os.path.splitext
  os.path.splitunc os.path.normpath os.makedirs
- mercurial.windows.normcase
- mercurial.util.normcase
  mercurial.util.endswithsep mercurial.util.splitpath mercurial.util.checkcase
  mercurial.util.fspath mercurial.util.pconvert mercurial.util.normpath
  mercurial.util.checkwinfilename mercurial.util.checkosfilename'''
diff --git a/mercurial/encoding.py b/mercurial/encoding.py
--- a/mercurial/encoding.py
+++ b/mercurial/encoding.py
@@ -171,3 +171,22 @@ def lower(s):
         return lu.encode(encoding)
     except UnicodeError:
         return s.lower() # we don't know how to fold this except in ASCII
+    except LookupError, k:
+        raise error.Abort(k, hint="please check your locale settings")
+
+def upper(s):
+    "best-effort encoding-aware case-folding of local string s"
+    try:
+        if isinstance(s, localstr):
+            u = s._utf8.decode("utf-8")
+        else:
+            u = s.decode(encoding, encodingmode)
+
+        uu = u.upper()
+        if u == uu:
+            return s # preserve localstring
+        return uu.encode(encoding)
+    except UnicodeError:
+        return s.upper() # we don't know how to fold this except in ASCII
+    except LookupError, k:
+        raise error.Abort(k, hint="please check your locale settings")
diff --git a/mercurial/posix.py b/mercurial/posix.py
--- a/mercurial/posix.py
+++ b/mercurial/posix.py
@@ -164,6 +164,9 @@ def samedevice(fpath1, fpath2):
     st2 = os.lstat(fpath2)
     return st1.st_dev == st2.st_dev
 
+encodinglower = None
+encodingupper = None
+
 # os.path.normcase is a no-op, which doesn't help us on non-native filesystems
 def normcase(path):
     return path.lower()
diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -24,6 +24,9 @@ if os.name == 'nt':
 else:
     import posix as platform
 
+platform.encodinglower = encoding.lower
+platform.encodingupper = encoding.upper
+
 cachestat = platform.cachestat
 checkexec = platform.checkexec
 checklink = platform.checklink
diff --git a/mercurial/windows.py b/mercurial/windows.py
--- a/mercurial/windows.py
+++ b/mercurial/windows.py
@@ -131,8 +131,11 @@ def localpath(path):
 def normpath(path):
     return pconvert(os.path.normpath(path))
 
+encodinglower = None
+encodingupper = None
+
 def normcase(path):
-    return path.upper()
+    return encodingupper(path)
 
 def realpath(path):
     '''