diff --git a/bookwyrm/tests/views/test_shelf.py b/bookwyrm/tests/views/test_shelf.py
index d873edc6..0d7d01cb 100644
--- a/bookwyrm/tests/views/test_shelf.py
+++ b/bookwyrm/tests/views/test_shelf.py
@@ -105,7 +105,7 @@ class ShelfViews(TestCase):
         shelf.refresh_from_db()
 
         self.assertEqual(shelf.name, "cool name")
-        self.assertEqual(shelf.identifier, "testshelf-%d" % shelf.id)
+        self.assertEqual(shelf.identifier, f"testshelf-{shelf.id}")
 
     def test_edit_shelf_name_not_editable(self, *_):
         """can't change the name of an non-editable shelf"""
diff --git a/bookwyrm/views/shelf.py b/bookwyrm/views/shelf.py
index 5d1008d0..6e75cc99 100644
--- a/bookwyrm/views/shelf.py
+++ b/bookwyrm/views/shelf.py
@@ -146,7 +146,7 @@ def shelve(request):
 
     # first we need to remove from the specified shelf
     change_from_current_identifier = request.POST.get("change-shelf-from")
-    if not change_from_current_identifier:
+    if change_from_current_identifier:
         # find the shelfbook obj and delete it
         get_object_or_404(
             models.ShelfBook,