diff --git a/webp_to_png/__main__.pyw b/webp_to_png/__main__.pyw
index ebe92ed..c39f9ef 100644
--- a/webp_to_png/__main__.pyw
+++ b/webp_to_png/__main__.pyw
@@ -12,7 +12,7 @@ layout = [
 window = sg.Window("批量webp格式转化为png格式 -by Zengtudor",layout,size=(800,400),resizable=True)
 bar = window["bar"]
 
-def main():
+def main() -> None:
     while True:
         ret = window.read()
         if ret: