diff --git a/mitmproxy/io_compat.py b/mitmproxy/io_compat.py
index dd0c12d66..8f89b86e9 100644
--- a/mitmproxy/io_compat.py
+++ b/mitmproxy/io_compat.py
@@ -90,10 +90,12 @@ def convert_100_200(data):
     data["version"] = (2, 0, 0)
     return data
 
+
 def convert_200_300(data):
     data["version"] = (3, 0, 0)
     return data
 
+
 def _convert_dict_keys(o: Any) -> Any:
     if isinstance(o, dict):
         return {strutils.always_str(k): _convert_dict_keys(v) for k, v in o.items()}