diff --git a/src/black/files.py b/src/black/files.py
index 8e1e6efb437..a33c36f040f 100644
--- a/src/black/files.py
+++ b/src/black/files.py
@@ -212,7 +212,7 @@ def gen_python_files(
                 extend_exclude,
                 force_exclude,
                 report,
-                gitignore + get_gitignore(child),
+                gitignore + get_gitignore(child) if gitignore else None,
             )
 
         elif child.is_file():