diff --git a/remotefilelog/__init__.py b/remotefilelog/__init__.py
--- a/remotefilelog/__init__.py
+++ b/remotefilelog/__init__.py
@@ -955,6 +955,7 @@
 @command('prefetch', [
     ('r', 'rev', [], _('prefetch the specified revisions'), _('REV')),
     ('', 'repack', False, _('run repack after prefetch')),
+    ('b', 'base', '', _("rev that is assumed to already be local")),
     ] + commands.walkopts, _('hg prefetch [OPTIONS] [FILE...]'))
 def prefetch(ui, repo, *pats, **opts):
     """prefetch file revisions from the server
@@ -987,7 +988,11 @@
 
     revs = scmutil.revrange(repo, opts.get('rev'))
 
-    repo.prefetch(revs, pats=pats, opts=opts)
+    base = opts.get('base')
+    if not base:
+        base = None
+
+    repo.prefetch(revs, base, pats, opts)
 
     # Run repack in background
     if opts.get('repack'):
diff --git a/tests/test-remotefilelog-prefetch.t b/tests/test-remotefilelog-prefetch.t
--- a/tests/test-remotefilelog-prefetch.t
+++ b/tests/test-remotefilelog-prefetch.t
@@ -35,6 +35,25 @@
   $ hg cat -r 0 x
   x
 
+# prefetch with base
+
+  $ hg prefetch -r 0::1 -b 0
+  2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob)
+
+  $ hg cat -r 1 x
+  x2
+  $ hg cat -r 1 y
+  y
+
+  $ hg cat -r 0 x
+  x
+  $ hg cat -r 0 z
+  z
+
+  $ hg prefetch -r 0::1 --base 0
+  $ hg prefetch -r 0::1 -b 1
+  $ hg prefetch -r 0::1
+
 # prefetch a range of revisions
 
   $ clearcache