diff --git a/project.py b/project.py
index 5a7a6ca..679dccc 100644
--- a/project.py
+++ b/project.py
@@ -1728,9 +1728,8 @@
     remote = self.GetRemote(self.remote.name)
     bundle_url = remote.url + '/clone.bundle'
     bundle_url = GitConfig.ForUser().UrlInsteadOf(bundle_url)
-    if GetSchemeFromUrl(bundle_url) in ('persistent-http', 'persistent-https'):
-      bundle_url = bundle_url[len('persistent-'):]
-    if GetSchemeFromUrl(bundle_url) not in ('http', 'https'):
+    if GetSchemeFromUrl(bundle_url) not in (
+        'http', 'https', 'persistent-http', 'persistent-https'):
       return False
 
     bundle_dst = os.path.join(self.gitdir, 'clone.bundle')
@@ -1779,9 +1778,11 @@
         os.remove(tmpPath)
     if 'http_proxy' in os.environ and 'darwin' == sys.platform:
       cmd += ['--proxy', os.environ['http_proxy']]
-    cookiefile = GitConfig.ForUser().GetString('http.cookiefile')
+    cookiefile = self._GetBundleCookieFile(srcUrl)
     if cookiefile:
       cmd += ['--cookie', cookiefile]
+    if srcUrl.startswith('persistent-'):
+      srcUrl = srcUrl[len('persistent-'):]
     cmd += [srcUrl]
 
     if IsTrace():
@@ -1804,7 +1805,7 @@
       return False
 
     if os.path.exists(tmpPath):
-      if curlret == 0 and os.stat(tmpPath).st_size > 16:
+      if curlret == 0 and self._IsValidBundle(tmpPath):
         os.rename(tmpPath, dstPath)
         return True
       else:
@@ -1813,6 +1814,41 @@
     else:
       return False
 
+  def _IsValidBundle(self, path):
+    try:
+      with open(path) as f:
+        if f.read(16) == '# v2 git bundle\n':
+          return True
+        else:
+          print("Invalid clone.bundle file; ignoring.", file=sys.stderr)
+          return False
+    except OSError:
+      return False
+
+  def _GetBundleCookieFile(self, url):
+    if url.startswith('persistent-'):
+      try:
+        p = subprocess.Popen(
+            ['git-remote-persistent-https', '-print_config', url],
+            stdin=subprocess.PIPE, stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE)
+        prefix = 'http.cookiefile='
+        for line in p.stdout:
+          line = line.strip()
+          if line.startswith(prefix):
+            return line[len(prefix):]
+        if p.wait():
+          line = iter(p.stderr).next()
+          if ' -print_config' in line:
+            pass  # Persistent proxy doesn't support -print_config.
+          else:
+            print(line + p.stderr.read(), file=sys.stderr)
+      except OSError as e:
+        if e.errno == errno.ENOENT:
+          pass  # No persistent proxy.
+        raise
+    return GitConfig.ForUser().GetString('http.cookiefile')
+
   def _Checkout(self, rev, quiet=False):
     cmd = ['checkout']
     if quiet: