diff --git a/tools/filters/convert_characters.py b/tools/filters/convert_characters.py
index 434a3b2f2af6..a0c9ae836160 100644
--- a/tools/filters/convert_characters.py
+++ b/tools/filters/convert_characters.py
@@ -22,7 +22,7 @@ def __main__():
         from_ch += "+"
 
     skipped = 0
-    with open(args[0], "rU") as fin:
+    with open(args[0]) as fin:
         with open(args[2], "w") as fout:
             for line in fin:
                 if options.strip: