diff --git a/my/core/dataset.py b/my/core/dataset.py
index dc6b197..037f057 100644
--- a/my/core/dataset.py
+++ b/my/core/dataset.py
@@ -4,6 +4,9 @@ from pathlib import Path
 def connect_readonly(db: Path):
     import dataset # type: ignore
     # see https://github.com/pudo/dataset/issues/136#issuecomment-128693122
+    # todo not sure if mode=ro has any benefit, but it doesn't work on read-only filesystems
+    # maybe it should autodetect readonly filesystems and apply this? not sure
     import sqlite3
-    creator = lambda: sqlite3.connect(f'file:{db}?mode=ro', uri=True)
+    # https://www.sqlite.org/draft/uri.html#uriimmutable
+    creator = lambda: sqlite3.connect(f'file:{db}?immutable=1', uri=True)
     return dataset.connect('sqlite:///', engine_kwargs={'creator': creator})