diff --git a/stand/aggridx.py b/stand/aggridx.py
index 0d8270e..f671f41 100644
--- a/stand/aggridx.py
+++ b/stand/aggridx.py
@@ -10,7 +10,10 @@ class aggridx(ui.aggrid):
 
     def row_id_to_index(self, row_id):
         data = self.options["rowData"]
-        return next(i for i, d in enumerate(data) if d["run"] == row_id) #TODO: "run" is not generic
+        try:
+            return next(i for i, d in enumerate(data) if d["run"] == row_id) #TODO: "run" is not generic
+        except StopIteration as e:
+            raise LookupError(f"run {row_id} not found") from e
 
     def set_cell_server(self, row_index, col_id, new_val):
         with self.props.suspend_updates():