diff --git a/src/calibre/devices/prs505/sony_cache.py b/src/calibre/devices/prs505/sony_cache.py
index cc12edd735..181a18bcf9 100644
--- a/src/calibre/devices/prs505/sony_cache.py
+++ b/src/calibre/devices/prs505/sony_cache.py
@@ -388,23 +388,35 @@ class XMLCache(object):
                 debug_print('WARNING: Some elements in the JSON cache were not'
                         ' found in the XML cache')
             records = [x for x in records if x is not None]
-            ids = set()
+            # Ensure each book has an ID.
             for rec in records:
-                id = rec.get('id', None)
-                if id is None:
+                if rec.get('id', None) is None:
                     rec.set('id', str(self.max_id(root)+1))
-                    id = rec.get('id', None)
-                ids.add(id)
-            # ids cannot contain None, so no reason to check
+            ids = [x.get('id', None) for x in records]
+            # Given that we set the ids, there shouldn't be any None's. But
+            # better to be safe...
+            if None in ids:
+                debug_print('WARNING: Some <text> elements do not have ids')
+                ids = [x for x in ids if x is not None]
 
             playlist = self.get_or_create_playlist(bl_index, category)
-            # Reduce ids to books not already in the playlist
+            # Get the books currently in the playlist. We will need them to be
+            # sure to put back any books that were manually added.
+            playlist_ids = []
             for item in playlist:
                 id_ = item.get('id', None)
                 if id_ is not None:
-                    ids.discard(id_)
-            # Add the books in ids that were not already in the playlist
-            for id_ in ids:
+                    playlist_ids.append(id_)
+            # Empty the playlist. We do this so that the playlist will have the
+            # order specified by get_collections
+            for item in list(playlist):
+                playlist.remove(item)
+
+            # Get a list of ids not known by get_collections
+            extra_ids = [x for x in playlist_ids if x not in ids]
+            # Rebuild the collection in the order specified by get_collections. Then
+            # add the ids that get_collections didn't know about.
+            for id_ in ids + extra_ids:
                 item = playlist.makeelement(
                         '{%s}item'%self.namespaces[bl_index],
                         nsmap=playlist.nsmap, attrib={'id':id_})
diff --git a/src/calibre/devices/usbms/books.py b/src/calibre/devices/usbms/books.py
index 6204ee3ccb..42d0f3c863 100644
--- a/src/calibre/devices/usbms/books.py
+++ b/src/calibre/devices/usbms/books.py
@@ -174,8 +174,8 @@ class CollectionsBookList(BookList):
                     if lpath not in collections_lpaths[category]:
                         collections_lpaths[category].add(lpath)
                         collections[category].append(book)
-                        if attr == 'series':
-                            series_categories.add(category)
+                    if attr == 'series':
+                        series_categories.add(category)
         # Sort collections
         for category, books in collections.items():
             def tgetter(x):