diff --git a/ui/src/views/Forecast.jsx b/ui/src/views/Forecast.jsx
index f3bc304..977294b 100644
--- a/ui/src/views/Forecast.jsx
+++ b/ui/src/views/Forecast.jsx
@@ -832,7 +832,11 @@ export default function Forecast({ sources = [], sourceId, versions = [], versio
   async function applyDepth(d) {
     const viewer = viewerRef.current
     if (!viewer) return
-    await viewer.restore({ group_by_depth: d })
+    // A partial restore({ group_by_depth }) on its own did nothing, so the whole
+    // config goes back with the field changed. table is dropped: it is loaded by
+    // reference, and a stale name in the config fails the lookup.
+    const { table: _t, ...cfg } = await viewer.save()
+    await viewer.restore({ ...cfg, group_by_depth: d })
     setExpandDepth(d)
   }