diff --git a/git-filter-repo b/git-filter-repo
index fba355a..41aca6a 100755
--- a/git-filter-repo
+++ b/git-filter-repo
@@ -2857,7 +2857,7 @@ class RepoFilter(object):
       except subprocess.CalledProcessError as e:
         output = None
       msg = ""
-      if os.path.isdir(output):
+      if output and os.path.isdir(output):
         msg = _("Note: when cloning local repositories, you need to pass\n"
                 "      --no-local to git clone to avoid this issue.\n")
       raise SystemExit(