diff --git a/charmcraft/extensions/flask.py b/charmcraft/extensions/flask.py
index 0b294a3d6..ec478328e 100644
--- a/charmcraft/extensions/flask.py
+++ b/charmcraft/extensions/flask.py
@@ -124,7 +124,7 @@ def get_root_snippet(self) -> Dict[str, Any]:
         }
         merging_fields = {
             "actions": ACTIONS,
-            "options": OPTIONS,
+            "config": {"options": OPTIONS},
         }
         incompatible_fields = ("devices", "extra-bindings", "storage")
         for incompatible_field in incompatible_fields: