diff --git a/packages/powersync_core/lib/src/crud.dart b/packages/powersync_core/lib/src/crud.dart
index 5a11ae4d..316d7874 100644
--- a/packages/powersync_core/lib/src/crud.dart
+++ b/packages/powersync_core/lib/src/crud.dart
@@ -82,6 +82,7 @@ class CrudEntry {
 
   factory CrudEntry.fromRow(sqlite.Row row) {
     final data = jsonDecode(row['data']);
+    assert(data['id'] is String, 'row ID should be of type String');
     return CrudEntry(row['id'], UpdateType.fromJsonChecked(data['op'])!,
         data['type'], data['id'], row['tx_id'], data['data']);
   }