diff --git a/src/calibre/ebooks/metadata/opf2.py b/src/calibre/ebooks/metadata/opf2.py
index ea8c114e10..162fce79df 100644
--- a/src/calibre/ebooks/metadata/opf2.py
+++ b/src/calibre/ebooks/metadata/opf2.py
@@ -1313,6 +1313,8 @@ class OPF(object):  # {{{
                      'isbn', 'tags', 'category', 'comments', 'book_producer',
                      'pubdate', 'user_categories', 'author_link_map'):
             val = getattr(mi, attr, None)
+            if attr == 'rating' and val:
+                val = float(val)
             is_null = val is None or val in ((), [], (None, None), {}) or (attr == 'rating' and val < 0.1)
             if is_null:
                 if apply_null and attr in {'series', 'tags', 'isbn', 'comments', 'publisher', 'rating'}:
diff --git a/src/calibre/ebooks/metadata/opf3.py b/src/calibre/ebooks/metadata/opf3.py
index dc1529f3f0..3c071fd2e3 100644
--- a/src/calibre/ebooks/metadata/opf3.py
+++ b/src/calibre/ebooks/metadata/opf3.py
@@ -744,7 +744,7 @@ def set_rating(root, prefixes, refines, val):
         if prop.lower() == pq:
             remove_element(meta, refines)
     if val:
-        create_rating(root, prefixes, '%.2g' % val)
+        create_rating(root, prefixes, '%.2g' % float(val))
 # }}}
 
 # Series {{{
@@ -1052,7 +1052,7 @@ def apply_metadata(root, mi, cover_prefix='', cover_data=None, apply_null=False,
         set_publisher(root, prefixes, refines, mi.publisher)
     if ok('tags'):
         set_tags(root, prefixes, refines, mi.tags)
-    if ok('rating') and mi.rating is not None and mi.rating > 0.1:
+    if ok('rating') and mi.rating is not None and float(mi.rating) > 0.1:
         set_rating(root, prefixes, refines, mi.rating)
     if ok('series'):
         set_series(root, prefixes, refines, mi.series, mi.series_index or 1)