diff -r 176b7d42e6cc -r c564dbb2a6d5 mercurial/commands.py
--- a/mercurial/commands.py	Thu Sep 17 21:51:55 2009 +0200
+++ b/mercurial/commands.py	Thu Sep 17 21:52:08 2009 +0200
@@ -3047,7 +3047,10 @@
     if not rev:
         rev = node
 
-    if not clean and check:
+    if check and clean:
+        raise util.Abort(_("cannot specify both -c/--check and -C/--clean"))
+
+    if check:
         # we could use dirty() but we can ignore merge and branch trivia
         c = repo[None]
         if c.modified() or c.added() or c.removed():