diff --git a/subcmds/init.py b/subcmds/init.py
index a3f3241..1fbe465 100644
--- a/subcmds/init.py
+++ b/subcmds/init.py
@@ -478,8 +478,13 @@ to update the working directory files.
 
     # Check this here, else manifest will be tagged "not new" and init won't be
     # possible anymore without removing the .repo/manifests directory.
-    if opt.archive and opt.mirror:
-      self.OptionParser.error('--mirror and --archive cannot be used together.')
+    if opt.mirror:
+      if opt.archive:
+        self.OptionParser.error('--mirror and --archive cannot be used '
+                                'together.')
+      if opt.use_superproject is not None:
+        self.OptionParser.error('--mirror and --use-superproject cannot be '
+                                'used together.')
 
     if opt.standalone_manifest and (
         opt.manifest_branch or opt.manifest_name != 'default.xml'):
diff --git a/subcmds/sync.py b/subcmds/sync.py
index 1d778e1..ee7e4a8 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -986,6 +986,10 @@ later is required to fix a server side protocol bug.
 
     load_local_manifests = not self.manifest.HasLocalManifests
     use_superproject = git_superproject.UseSuperproject(opt, self.manifest)
+    if self.manifest.IsMirror or self.manifest.IsArchive:
+      # Don't use superproject, because we have no working tree.
+      use_superproject = False
+      print('Defaulting to no-use-superproject because there is no working tree.')
     superproject_logging_data = {
         'superproject': use_superproject,
         'haslocalmanifests': bool(self.manifest.HasLocalManifests),