diff -r ba5e71770db2 -r 341868ef0cf6 mercurial/scmutil.py
--- a/mercurial/scmutil.py	Wed Oct 24 23:09:31 2012 +0200
+++ b/mercurial/scmutil.py	Tue Feb 05 16:22:53 2013 -0800
@@ -34,6 +34,11 @@
     for c in (':', '\0', '\n', '\r'):
         if c in lbl:
             raise util.Abort(_("%r cannot be used in a name") % c)
+    try:
+        int(lbl)
+        raise util.Abort(_("a %s cannot have an integer as its name") % kind)
+    except ValueError:
+        pass
 
 def checkfilename(f):
     '''Check that the filename f is an acceptable filename for a tracked file'''