diff --git a/src/gridSystem.ts b/src/gridSystem.ts
index b41e1697a..c3e47a6e5 100644
--- a/src/gridSystem.ts
+++ b/src/gridSystem.ts
@@ -232,7 +232,7 @@ export const gridSystem = /*#__PURE__*/ u.system(
 
             if (itemWidth === 0) {
               const startIndex = getInitialTopMostItemIndexNumber(initialTopMostItemIndex, totalCount)
-              const endIndex = Math.max(startIndex + initialItemCount - 1, 0)
+              const endIndex = startIndex + Math.max(initialItemCount - 1, 0)
               return buildProbeGridState(buildItems(startIndex, endIndex, data))
             }
 
diff --git a/test/Grid.test.tsx b/test/Grid.test.tsx
index 696375094..9ed1f6dcd 100644
--- a/test/Grid.test.tsx
+++ b/test/Grid.test.tsx
@@ -43,6 +43,24 @@ describe('Grid', () => {
     expect(listParent.textContent).toBe('Item 0')
   })
 
+  it('renders a probe item initially with the initialTopMostItemIndex', () => {
+    act(() => {
+      ReactDOM.createRoot(container).render(<VirtuosoGrid totalCount={20000} initialTopMostItemIndex={10} />)
+    })
+
+    const scroller = container.firstElementChild as any
+    const viewport = scroller.firstElementChild
+    const listParent = viewport.firstElementChild
+
+    act(() => {
+      scroller.triggerScroll({ scrollTop: 0, scrollHeight: 700, viewportHeight: 200 })
+      viewport.triggerResize({ getBoundingClientRect: () => ({ height: 700 }) })
+    })
+
+    expect(listParent.children).toHaveLength(1)
+    expect(listParent.textContent).toBe('Item 10')
+  })
+
   describe('data list', () => {
     let scroller: any
     let viewport: any