diff --git a/cmd/actionExecute.go b/cmd/actionExecute.go
index 29d8d9b..d2623da 100644
--- a/cmd/actionExecute.go
+++ b/cmd/actionExecute.go
@@ -90,8 +90,7 @@ func actionExecute() {
 		log.Fatalf("error: expected action to produce exactly one item, got %d", len(res))
 	}
 	newItem := res[0]
-	newItem.Active = item.Active   // These fields can't
-	newItem.Created = item.Created // be updated by actions
+	core.BackfillItem(&newItem, &item)
 
 	if actionExecuteDiff {
 		if item.Title != newItem.Title {
@@ -119,5 +118,7 @@ func actionExecute() {
 		return
 	}
 
-	// TODO
+	if err = core.UpdateItems(db, []core.Item{newItem}); err != nil {
+		log.Fatalf("error: failed to update item: %v", err)
+	}
 }
diff --git a/core/source.go b/core/source.go
index f220220..96c035b 100644
--- a/core/source.go
+++ b/core/source.go
@@ -82,6 +82,56 @@ func AddItems(db *DB, items []Item) error {
 	})
 }
 
+// Set fields in the new item to match the old item where the new item's fields are zero-valued.
+// This allows sources to omit fields and let an action set them without a later fetch overwriting
+// the value from the action, e.g. an on-create action archiving a page and setting the link to
+// point to the archive.
+func BackfillItem(new *Item, old *Item) {
+	new.Active = old.Active
+	new.Created = old.Created
+	if new.Author == "" {
+		new.Author = old.Author
+	}
+	if new.Body == "" {
+		new.Body = old.Body
+	}
+	if new.Link == "" {
+		new.Link = old.Link
+	}
+	if new.Time == 0 {
+		new.Time = old.Time
+	}
+	if new.Title == "" {
+		new.Title = old.Title
+	}
+}
+
+func UpdateItems(db *DB, items []Item) error {
+	return db.Transact(func(tx *sql.Tx) error {
+		stmt, err := tx.Prepare(`
+			update items
+			set
+				title = ?,
+				author = ?,
+				body = ?,
+				link = ?,
+				time = ?
+			where source = ?
+			and id = ?
+		`)
+		if err != nil {
+			return err
+		}
+		for _, item := range items {
+			_, err = stmt.Exec(item.Title, item.Author, item.Body, item.Link, item.Time, item.Source, item.Id)
+			if err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+}
+
 // Deactivate an item, returning its previous active state.
 func DeactivateItem(db *DB, source string, id string) (bool, error) {
 	row := db.QueryRow(`
@@ -197,8 +247,10 @@ func UpdateWithFetchedItems(db *DB, source string, items []Item) (int, int, erro
 		return 0, 0, err
 	}
 	existingIds := map[string]bool{}
+	existingItemsById := map[string]*Item{}
 	for _, item := range existingItems {
 		existingIds[item.Id] = true
+		existingItemsById[item.Id] = &item
 	}
 
 	// Split the fetch into adds and updates
@@ -218,7 +270,12 @@ func UpdateWithFetchedItems(db *DB, source string, items []Item) (int, int, erro
 	}
 
 	// Bulk update the existing items
-	// TODO
+	for _, item := range updatedItems {
+		BackfillItem(&item, existingItemsById[item.Id])
+	}
+	if err = UpdateItems(db, updatedItems); err != nil {
+		return 0, 0, err
+	}
 
 	// Get the list of expired items
 	fetchedIds := map[string]bool{}