diff --git a/src/calibre/ebooks/metadata/opf2.py b/src/calibre/ebooks/metadata/opf2.py
index 92287589eb..1950ee4621 100644
--- a/src/calibre/ebooks/metadata/opf2.py
+++ b/src/calibre/ebooks/metadata/opf2.py
@@ -1430,7 +1430,10 @@ def metadata_to_opf(mi, as_string=True, default_lang=None):
         elem = metadata.makeelement(tag, attrib=attrib)
         elem.tail = '\n'+(' '*8)
         if text:
-            elem.text = text.strip()
+            try:
+                elem.text = text.strip()
+            except ValueError:
+                elem.text = clean_ascii_chars(text.strip())
         metadata.append(elem)
 
     factory(DC('title'), mi.title)