--- a/mercurial/obsolete.py	Wed May 31 20:07:08 2017 -0700
+++ b/mercurial/obsolete.py	Thu May 25 16:50:23 2017 +0200
@@ -446,8 +446,8 @@
     diskversion = _unpack('>B', data[off:off + 1])[0]
     off += 1
     if diskversion not in formats:
-        raise error.Abort(_('parsing obsolete marker: unknown version %r')
-                         % diskversion)
+        msg = _('parsing obsolete marker: unknown version %r') % diskversion
+        raise error.UnknownVersion(msg, version=diskversion)
     return diskversion, formats[diskversion][0](data, off)
 
 def encodemarkers(markers, addheader=False, version=_fm0version):