--- a/tools/mercurial/hgsetup/config.py
+++ b/tools/mercurial/hgsetup/config.py
@@ -204,8 +204,23 @@ class MercurialConfig(object):
     def clear_legacy_bugzilla_credentials(self):
         if 'bugzilla' not in self._c:
             return
 
         b = self._c['bugzilla']
         for k in ('password', 'userid', 'cookie'):
             if k in b:
                 del b[k]
+
+    def have_clonebundles(self):
+        return 'clonebundles' in self._c.get('experimental', {})
+
+    def activate_clonebundles(self):
+        exp = self._c.setdefault('experimental', {})
+        exp['clonebundles'] = 'true'
+
+        # bundleclone is redundant with clonebundles. Remove it if it
+        # is installed.
+        ext = self._c.get('extensions', {})
+        try:
+            del ext['bundleclone']
+        except KeyError:
+            pass

--- a/tools/mercurial/hgsetup/wizard.py
+++ b/tools/mercurial/hgsetup/wizard.py
@@ -206,16 +206,25 @@ try syntax and pushes it to the try serv
 to be used in concert with other tools generating try syntax so that
 they can push to try without depending on mq or other workarounds.
 
 (Relevant config option: extensions.push-to-try)
 
 Would you like to activate push-to-try
 '''.strip()
 
+CLONEBUNDLES_INFO = '''
+Mercurial 3.6 and hg.mozilla.org support transparently cloning from a CDN,
+making clones faster and more reliable.
+
+(Relevant config option: experimental.clonebundles)
+
+Would you like to activate this feature and have faster clones
+'''.strip()
+
 BUNDLECLONE_MINIMUM_VERSION = LooseVersion('3.1')
 
 BUNDLECLONE_INFO = '''
 The bundleclone extension makes cloning faster and saves server resources.
 
 We highly recommend you activate this extension.
 
 (Relevant config option: extensions.bundleclone)
@@ -354,17 +363,23 @@ class MercurialSetupWizard(object):
         self.prompt_external_extension(c, 'bzexport', BZEXPORT_INFO)
 
         if hg_version >= BZPOST_MINIMUM_VERSION:
             self.prompt_external_extension(c, 'bzpost', BZPOST_INFO)
 
         if hg_version >= FIREFOXTREE_MINIMUM_VERSION:
             self.prompt_external_extension(c, 'firefoxtree', FIREFOXTREE_INFO)
 
-        if hg_version >= BUNDLECLONE_MINIMUM_VERSION:
+        # Functionality from bundleclone is experimental in Mercurial 3.6.
+        # There was a bug in 3.6, so look for 3.6.1.
+        if hg_version >= LooseVersion('3.6.1'):
+            if not c.have_clonebundles() and self._prompt_yn(CLONEBUNDLES_INFO):
+                c.activate_clonebundles()
+                print('Enabled the clonebundles feature.\n')
+        elif hg_version >= BUNDLECLONE_MINIMUM_VERSION:
             self.prompt_external_extension(c, 'bundleclone', BUNDLECLONE_INFO)
 
         if hg_version >= PUSHTOTRY_MINIMUM_VERSION:
             self.prompt_external_extension(c, 'push-to-try', PUSHTOTRY_INFO)
 
         if 'mq' in c.extensions:
             self.prompt_external_extension(c, 'mqext', MQEXT_INFO)