diff --git a/bookwyrm/models/base_model.py b/bookwyrm/models/base_model.py
index 430097c0..1253e7a5 100644
--- a/bookwyrm/models/base_model.py
+++ b/bookwyrm/models/base_model.py
@@ -281,4 +281,6 @@ class OrderedCollectionMixin(OrderedCollectionPageMixin):
 
     def to_activity(self, **kwargs):
         ''' an ordered collection of the specified model queryset  '''
+        if not self.collection_queryset.ordered:
+            raise RuntimeError('collection_queryset must be ordered')
         return self.to_ordered_collection(self.collection_queryset, **kwargs)
diff --git a/bookwyrm/models/shelf.py b/bookwyrm/models/shelf.py
index a06f78dc..84575137 100644
--- a/bookwyrm/models/shelf.py
+++ b/bookwyrm/models/shelf.py
@@ -39,7 +39,7 @@ class Shelf(OrderedCollectionMixin, BookWyrmModel):
     @property
     def collection_queryset(self):
         ''' list of books for this shelf, overrides OrderedCollectionMixin  '''
-        return self.books.all()
+        return self.books.all().order_by('shelfbook')
 
     def get_remote_id(self):
         ''' shelf identifier instead of id '''
@@ -90,3 +90,4 @@ class ShelfBook(ActivitypubMixin, BookWyrmModel):
         ''' an opinionated constraint!
             you can't put a book on shelf twice '''
         unique_together = ('book', 'shelf')
+        ordering = ('-created_date',)