diff --git a/grub/__init__.py b/grub/__init__.py
index 5c5f977..3cd293d 100644
--- a/grub/__init__.py
+++ b/grub/__init__.py
@@ -14,7 +14,7 @@ MODULES = {
 
 
 def make_image(image_format: str, image_path: str, modules: list[str],
-               memdisk_path: str, pubkey_path: str=None) -> None:
+               memdisk_path: str, pubkey_path: str = None) -> None:
     args = [
         ('grub-mkimage'),
         ('--compress', COMPRESSION),