--- a/hgext3rd/evolve/obsexchange.py	Tue Nov 07 12:10:22 2017 +0100
+++ b/hgext3rd/evolve/obsexchange.py	Tue Nov 07 12:36:27 2017 +0100
@@ -27,6 +27,8 @@
     wireproto,
 )
 
+from mercurial.hgweb import common as hgwebcommon
+
 from . import (
     exthelper,
     utility,
@@ -197,14 +199,23 @@
 abortmsg = "won't exchange obsmarkers through pushkey"
 hint = "upgrade your client or server to use the bundle2 protocol"
 
+class HTTPCompatibleAbort(hgwebcommon.ErrorResponse, error.Abort):
+    def __init__(self, message, code, hint=None):
+        # initialisation of each class is a bit messy.
+        # We explicitly do the dispatch
+        hgwebcommon.ErrorResponse.__init__(self, 410, message)
+        error.Abort.__init__(self, message, hint=hint)
+
 def forbidpushkey(repo=None, key=None, old=None, new=None):
     """prevent exchange through pushkey"""
-    raise error.Abort(abortmsg, hint=hint)
+    err = HTTPCompatibleAbort(abortmsg, 410, hint=hint)
+    raise err
 
 def forbidlistkey(repo=None, key=None, old=None, new=None):
     """prevent exchange through pushkey"""
     if obsolete.isenabled(repo, obsolete.exchangeopt):
-        raise error.Abort(abortmsg, hint=hint)
+        err = HTTPCompatibleAbort(abortmsg, 410, hint=hint)
+        raise err
     return {}
 
 @eh.uisetup

--- a/tests/test-wireproto.t	Tue Nov 07 12:10:22 2017 +0100
+++ b/tests/test-wireproto.t	Tue Nov 07 12:36:27 2017 +0100
@@ -200,7 +200,7 @@
 Check we cannot use pushkey for marker exchange anymore
 
   $ hg debugpushkey http://localhost:$HGPORT/ obsolete
-  abort: HTTP Error 500: Internal Server Error
+  abort: HTTP Error 410: won't exchange obsmarkers through pushkey
   [255]
   $ hg debugpushkey ssh://user@dummy/server obsolete
   remote: abort: won't exchange obsmarkers through pushkey