diff --git a/test/focus-lens.test.tsx b/test/focus-lens.test.tsx
index 82e8289..e9ecdfa 100644
--- a/test/focus-lens.test.tsx
+++ b/test/focus-lens.test.tsx
@@ -32,3 +32,54 @@ it('focus on an atom works', async () => {
   await findByText('count: 1')
   await findByText('bigAtom: {"a":1}')
 })
+
+it('double-focus on an atom works', async () => {
+  const bigAtom = atom({ a: { b: 0 } })
+  const atomA = focus(bigAtom, optic => optic.prop('a'))
+  const atomB = focus(atomA, optic => optic.prop('b'))
+
+  const Counter: React.FC = () => {
+    const [bigAtomValue, setBigAtom] = useAtom(bigAtom)
+    const [atomAValue, setAtomA] = useAtom(atomA)
+    const [atomBValue, setAtomB] = useAtom(atomB)
+    return (
+      <>
+        <div>bigAtom: {JSON.stringify(bigAtomValue)}</div>
+        <div>atomA: {JSON.stringify(atomAValue)}</div>
+        <div>atomB: {JSON.stringify(atomBValue)}</div>
+        <button onClick={() => setBigAtom(v => ({ a: { b: v.a.b + 1 } }))}>
+          inc bigAtom
+        </button>
+        <button onClick={() => setAtomA(v => ({ b: v.b + 2 }))}>
+          inc atomA
+        </button>
+        <button onClick={() => setAtomB(v => v + 3)}>inc atomB</button>
+      </>
+    )
+  }
+
+  const { getByText, findByText } = rtl.render(
+    <Provider>
+      <Counter />
+    </Provider>,
+  )
+
+  await findByText('bigAtom: {"a":{"b":0}}')
+  await findByText('atomA: {"b":0}')
+  await findByText('atomB: 0')
+
+  rtl.fireEvent.click(getByText('inc bigAtom'))
+  await findByText('bigAtom: {"a":{"b":1}}')
+  await findByText('atomA: {"b":1}')
+  await findByText('atomB: 1')
+
+  rtl.fireEvent.click(getByText('inc atomA'))
+  await findByText('bigAtom: {"a":{"b":3}}')
+  await findByText('atomA: {"b":3}')
+  await findByText('atomB: 3')
+
+  rtl.fireEvent.click(getByText('inc atomB'))
+  await findByText('bigAtom: {"a":{"b":6}}')
+  await findByText('atomA: {"b":6}')
+  await findByText('atomB: 6')
+})
diff --git a/test/focus-prism.test.tsx b/test/focus-prism.test.tsx
index 46c2911..1f176b8 100644
--- a/test/focus-prism.test.tsx
+++ b/test/focus-prism.test.tsx
@@ -5,7 +5,7 @@ import { focus } from '../src/index'
 
 it('updates prisms', async () => {
   const bigAtom = atom<{ a: number | undefined }>({ a: 5 })
-  const aAtom = focus(bigAtom, optic => optic.prop('a'))
+  const aAtom = focus(bigAtom, optic => optic.prop('a').optional())
 
   const Counter: React.FC = () => {
     const [count, setCount] = useAtom(aAtom)
@@ -25,10 +25,40 @@ it('updates prisms', async () => {
     </Provider>,
   )
 
-  await findByText('count: 0')
-  await findByText('bigAtom: {"a":0}')
+  await findByText('count: 5')
+  await findByText('bigAtom: {"a":5}')
 
   rtl.fireEvent.click(getByText('button'))
-  await findByText('count: 1')
-  await findByText('bigAtom: {"a":1}')
+  await findByText('count: 6')
+  await findByText('bigAtom: {"a":6}')
+})
+
+it('atoms that focus on no values are not updated', async () => {
+  const bigAtom = atom<{ a?: number }>({})
+  const aAtom = focus(bigAtom, optic => optic.prop('a').optional())
+
+  const Counter: React.FC = () => {
+    const [count, setCount] = useAtom(aAtom)
+    const [bigAtomValue] = useAtom(bigAtom)
+    return (
+      <>
+        <div>bigAtom: {JSON.stringify(bigAtomValue)}</div>
+        <div>count: {JSON.stringify(count)}</div>
+        <button onClick={() => setCount(c => c + 1)}>button</button>
+      </>
+    )
+  }
+
+  const { getByText, findByText } = rtl.render(
+    <Provider>
+      <Counter />
+    </Provider>,
+  )
+
+  await findByText('count:')
+  await findByText('bigAtom: {}')
+
+  rtl.fireEvent.click(getByText('button'))
+  await findByText('count:')
+  await findByText('bigAtom: {}')
 })