diff --git a/Lib/gzip.py b/Lib/gzip.py
index 8002b43..ee0cbed 100644
--- a/Lib/gzip.py
+++ b/Lib/gzip.py
@@ -583,7 +583,7 @@ def main():
                 g = sys.stdout.buffer
             else:
                 if arg[-3:] != ".gz":
-                    sys.exit("filename doesn't end in .gz:", repr(arg))
+                    sys.exit(f"filename doesn't end in .gz: {arg!r}")
                 f = open(arg, "rb")
                 g = builtins.open(arg[:-3], "wb")
         else: