diff --git a/src/lib/__tests__/InstantSearch-test.js b/src/lib/__tests__/InstantSearch-test.js
index 737bc19b15..b552c0532e 100644
--- a/src/lib/__tests__/InstantSearch-test.js
+++ b/src/lib/__tests__/InstantSearch-test.js
@@ -239,6 +239,24 @@ describe('InstantSearch', () => {
 
     expect(search.insightsClient).toBe(insightsClient);
   });
+
+  it("exposes helper's last results", async () => {
+    const searchClient = createSearchClient();
+
+    const search = new InstantSearch({
+      indexName: 'indexName',
+      searchClient,
+    });
+
+    expect(search.helper).toBe(null);
+
+    search.start();
+
+    await runAllMicroTasks();
+
+    // could be null if we don't pretend the main helper is the one who searched
+    expect(search.helper.lastResults).not.toBe(null);
+  });
 });
 
 describe('addWidget(s)', () => {
diff --git a/src/widgets/index/index.ts b/src/widgets/index/index.ts
index 5e6b81d0b4..2b1c245f7b 100644
--- a/src/widgets/index/index.ts
+++ b/src/widgets/index/index.ts
@@ -459,11 +459,17 @@ See https://www.algolia.com/doc/guides/building-search-ui/widgets/customize-an-e
         }
       });
 
-      derivedHelper.on('result', () => {
+      derivedHelper.on('result', ({ results }) => {
         // The index does not render the results it schedules a new render
         // to let all the other indices emit their own results. It allows us to
         // run the render process in one pass.
         instantSearchInstance.scheduleRender();
+
+        // the derived helper is the one which actually searches, but the helper
+        // which is exposed e.g. via instance.helper, doesn't search, and thus
+        // does not have access to lastResults, which it used to in pre-federated
+        // search behavior.
+        helper!.lastResults = results;
       });
 
       localWidgets.forEach(widget => {