diff --git a/src/calibre/db/cache.py b/src/calibre/db/cache.py
index 283773ac58..28058d7e8a 100644
--- a/src/calibre/db/cache.py
+++ b/src/calibre/db/cache.py
@@ -223,7 +223,7 @@ class Cache(object):
             good_formats = None
         else:
             mi.format_metadata = FormatMetadata(self, book_id, formats)
-            good_formats = FormatsList(formats, mi.format_metadata)
+            good_formats = FormatsList(sorted(formats), mi.format_metadata)
         # These three attributes are returned by the db2 get_metadata(),
         # however, we dont actually use them anywhere other than templates, so
         # they have been removed, to avoid unnecessary overhead. The templates
diff --git a/src/calibre/db/lazy.py b/src/calibre/db/lazy.py
index 166627c438..73260c8ae7 100644
--- a/src/calibre/db/lazy.py
+++ b/src/calibre/db/lazy.py
@@ -175,7 +175,7 @@ def fmt_getter(field):
                 if m:
                     format_metadata[fmt] = m
         if field == 'formats':
-            return list(format_metadata) or None
+            return sorted(format_metadata) or None
         return format_metadata
     return func
 
diff --git a/src/calibre/db/tests/reading.py b/src/calibre/db/tests/reading.py
index 66b1dacec4..56866f5aa7 100644
--- a/src/calibre/db/tests/reading.py
+++ b/src/calibre/db/tests/reading.py
@@ -478,7 +478,7 @@ class ReadingTest(BaseTest):
             for field in STANDARD_METADATA_FIELDS | {'#series_index'}:
                 f = lambda x: x
                 if field == 'formats':
-                    f = lambda x: x if x is None else set(x)
+                    f = lambda x: x if x is None else tuple(x)
                 self.assertEqual(f(getattr(mi, field)), f(getattr(pmi, field)),
                                 'Standard field: %s not the same for book %s' % (field, book_id))
                 self.assertEqual(mi.format_field(field), pmi.format_field(field),