diff --git a/src/calibre/ebooks/oeb/polish/images.py b/src/calibre/ebooks/oeb/polish/images.py
index 31a203f2c0..23d06d979f 100644
--- a/src/calibre/ebooks/oeb/polish/images.py
+++ b/src/calibre/ebooks/oeb/polish/images.py
@@ -9,7 +9,7 @@ from functools import partial
 from threading import Thread, Event
 from Queue import Queue, Empty
 
-from calibre import detect_ncpus, human_readable
+from calibre import detect_ncpus, human_readable, force_unicode, filesystem_encoding
 
 class Worker(Thread):
 
@@ -82,6 +82,7 @@ def compress_images(container, report=None, names=None, jpeg_quality=None, progr
     queue.join()
     before_total = after_total = 0
     for name, (ok, res) in results.iteritems():
+        name = force_unicode(name, filesystem_encoding)
         if ok:
             before, after = res
             if before != after:
diff --git a/src/calibre/gui2/tweak_book/polish.py b/src/calibre/gui2/tweak_book/polish.py
index ab78d82f92..9a2278521b 100644
--- a/src/calibre/gui2/tweak_book/polish.py
+++ b/src/calibre/gui2/tweak_book/polish.py
@@ -15,7 +15,7 @@ from PyQt5.Qt import (
     QProgressBar, pyqtSignal
 )
 
-from calibre import human_readable, fit_image
+from calibre import human_readable, fit_image, force_unicode
 from calibre.ebooks.oeb.polish.main import CUSTOMIZATION
 from calibre.gui2.tweak_book import tprefs, current_container, set_current_container
 from calibre.gui2.tweak_book.widgets import Dialog
@@ -56,7 +56,8 @@ def get_customization(action, name, parent):
 
 def format_report(title, report):
     from calibre.ebooks.markdown import markdown
-    return markdown('# %s\n\n'%title + '\n\n'.join(report), output_format='html4')
+    report = [force_unicode(line) for line in report]
+    return markdown('# %s\n\n'%force_unicode(title) + '\n\n'.join(report), output_format='html4')
 
 def show_report(changed, title, report, parent, show_current_diff):
     report = format_report(title, report)