diff --git a/tools/lister.py b/tools/lister.py
index f0365722f0..3f3b0a63a5 100755
--- a/tools/lister.py
+++ b/tools/lister.py
@@ -76,8 +76,8 @@ def list_files(targets=[], ftypes=[], use_shebang=True, modified_only=False,
     # throw away empty lines and non-files (like symlinks)
     files = list(filter(os.path.isfile, files_gen))
 
-    result_dict = defaultdict(list) # type: Dict[str, List[str]]
-    result_list = [] # type: List[str]
+    result_dict = defaultdict(list)  # type: Dict[str, List[str]]
+    result_list = []  # type: List[str]
 
     for fpath in files:
         # this will take a long time if exclude is very large