diff --git a/remotefilelog/remotefilelogserver.py b/remotefilelog/remotefilelogserver.py
--- a/remotefilelog/remotefilelogserver.py
+++ b/remotefilelog/remotefilelogserver.py
@@ -6,6 +6,7 @@
 # GNU General Public License version 2 or any later version.
 from __future__ import absolute_import
 
+from mercurial import ancestor
 from mercurial import changegroup, match, util, changelog, context
 from mercurial import store, error
 from mercurial import streamclone
@@ -483,8 +484,9 @@
 
             # Compute history
             history = []
-            for rev in fl.ancestors(list(fl.rev(n) for n in nodes),
-                                    inclusive=True):
+            for rev in ancestor.lazyancestors(fl.parentrevs,
+                                              [fl.rev(n) for n in nodes],
+                                              inclusive=True):
                 x, x, x, x, linkrev, p1, p2, node = fl.index[rev]
                 copyfrom = ''
                 p1node = fl.node(p1)