diff --git a/progressbar/bar.py b/progressbar/bar.py
index 36bd3caa..7ddd541b 100644
--- a/progressbar/bar.py
+++ b/progressbar/bar.py
@@ -51,7 +51,7 @@ def __init__(self, fd=sys.stderr, **kwargs):
 
     def update(self, *args, **kwargs):
         ProgressBarMixinBase.update(self, *args, **kwargs)
-        line = converters.to_str('\r' + self._format_line())
+        line = converters.to_unicode('\r' + self._format_line())
         self.fd.write(line)
 
     def finish(self, *args, **kwargs):  # pragma: no cover