--- a/mercurial/commands.py	Mon Jul 30 15:48:04 2012 +0200
+++ b/mercurial/commands.py	Mon Jul 30 19:26:05 2012 +0200
@@ -2067,17 +2067,31 @@
          _('[OBSOLETED [REPLACEMENT] [REPL... ]'))
 def debugobsolete(ui, repo, precursor=None, *successors, **opts):
     """create arbitrary obsolete marker"""
+    def parsenodeid(s):
+        try:
+            # We do not use revsingle/revrange functions here to accept
+            # arbitrary node identifiers, possibly not present in the
+            # local repository.
+            n = bin(s)
+            if len(n) != len(nullid):
+                raise TypeError()
+            return n
+        except TypeError:
+            raise util.Abort('changeset references must be full hexadecimal '
+                             'node identifiers')
+
     if precursor is not None:
         metadata = {}
         if 'date' in opts:
             metadata['date'] = opts['date']
         metadata['user'] = opts['user'] or ui.username()
-        succs = tuple(bin(succ) for succ in successors)
+        succs = tuple(parsenodeid(succ) for succ in successors)
         l = repo.lock()
         try:
             tr = repo.transaction('debugobsolete')
             try:
-                repo.obsstore.create(tr, bin(precursor), succs, 0, metadata)
+                repo.obsstore.create(tr, parsenodeid(precursor), succs, 0,
+                                     metadata)
                 tr.close()
             finally:
                 tr.release()

--- a/tests/test-obsolete.t	Mon Jul 30 15:48:04 2012 +0200
+++ b/tests/test-obsolete.t	Mon Jul 30 19:26:05 2012 +0200
@@ -31,6 +31,12 @@
 Killing a single changeset without replacement
 
   $ mkcommit kill_me
+  $ hg debugobsolete 0
+  abort: changeset references must be full hexadecimal node identifiers
+  [255]
+  $ hg debugobsolete '00'
+  abort: changeset references must be full hexadecimal node identifiers
+  [255]
   $ hg debugobsolete -d '0 0' `getid kill_me` -u babar
   $ hg debugobsolete
   97b7c2d76b1845ed3eb988cd612611e72406cef0 0 {'date': '0 0', 'user': 'babar'}