diff --git a/packages/@headlessui-react/CHANGELOG.md b/packages/@headlessui-react/CHANGELOG.md
index 1c6ba07023..4988bc105d 100644
--- a/packages/@headlessui-react/CHANGELOG.md
+++ b/packages/@headlessui-react/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Fix `ListboxOptions` being incorrectly marked as `inert` ([#3466](https://github.com/tailwindlabs/headlessui/pull/3466))
+- Fix crash when using `DisclosureButton` inside of a `DisclosurePanel` when the `Disclosure` is open by default ([#3465](https://github.com/tailwindlabs/headlessui/pull/3465))
 
 ## [2.1.5] - 2024-09-04
 
diff --git a/packages/@headlessui-react/src/components/disclosure/disclosure.test.tsx b/packages/@headlessui-react/src/components/disclosure/disclosure.test.tsx
index d32844943c..6b6626878d 100644
--- a/packages/@headlessui-react/src/components/disclosure/disclosure.test.tsx
+++ b/packages/@headlessui-react/src/components/disclosure/disclosure.test.tsx
@@ -337,6 +337,49 @@ describe('Rendering', () => {
       })
     )
 
+    it('should behave as a close button when used inside of the Disclosure.Panel', async () => {
+      render(
+        <Disclosure>
+          <Disclosure.Button>Open</Disclosure.Button>
+          <Disclosure.Panel>
+            <Disclosure.Button>Close</Disclosure.Button>
+          </Disclosure.Panel>
+        </Disclosure>
+      )
+
+      assertDisclosureButton({ state: DisclosureState.InvisibleUnmounted })
+      assertDisclosurePanel({ state: DisclosureState.InvisibleUnmounted })
+
+      await click(getByText('Open'))
+
+      assertDisclosureButton({ state: DisclosureState.Visible })
+      assertDisclosurePanel({ state: DisclosureState.Visible })
+
+      await click(getByText('Close'))
+
+      assertDisclosureButton({ state: DisclosureState.InvisibleUnmounted })
+      assertDisclosurePanel({ state: DisclosureState.InvisibleUnmounted })
+    })
+
+    it('should behave as a close button when used inside of the Disclosure.Panel (defaultOpen)', async () => {
+      render(
+        <Disclosure defaultOpen>
+          <Disclosure.Button>Open</Disclosure.Button>
+          <Disclosure.Panel>
+            <Disclosure.Button>Close</Disclosure.Button>
+          </Disclosure.Panel>
+        </Disclosure>
+      )
+
+      assertDisclosureButton({ state: DisclosureState.Visible })
+      assertDisclosurePanel({ state: DisclosureState.Visible })
+
+      await click(getByText('Close'))
+
+      assertDisclosureButton({ state: DisclosureState.InvisibleUnmounted })
+      assertDisclosurePanel({ state: DisclosureState.InvisibleUnmounted })
+    })
+
     describe('`type` attribute', () => {
       it('should set the `type` to "button" by default', async () => {
         render(
diff --git a/packages/@headlessui-react/src/components/disclosure/disclosure.tsx b/packages/@headlessui-react/src/components/disclosure/disclosure.tsx
index 2f3e522627..d7a5dd1425 100644
--- a/packages/@headlessui-react/src/components/disclosure/disclosure.tsx
+++ b/packages/@headlessui-react/src/components/disclosure/disclosure.tsx
@@ -299,9 +299,10 @@ function ButtonFn<TTag extends ElementType = typeof DEFAULT_BUTTON_TAG>(
   let buttonRef = useSyncRefs(
     internalButtonRef,
     ref,
-    !isWithinPanel
-      ? useEvent((element) => dispatch({ type: ActionTypes.SetButtonElement, element }))
-      : null
+    useEvent((element) => {
+      if (isWithinPanel) return
+      return dispatch({ type: ActionTypes.SetButtonElement, element })
+    })
   )
   let mergeRefs = useMergeRefsFn()
 
diff --git a/packages/@headlessui-react/src/components/popover/popover.tsx b/packages/@headlessui-react/src/components/popover/popover.tsx
index b1efa7eaf6..49a02f742d 100644
--- a/packages/@headlessui-react/src/components/popover/popover.tsx
+++ b/packages/@headlessui-react/src/components/popover/popover.tsx
@@ -535,24 +535,23 @@ function ButtonFn<TTag extends ElementType = typeof DEFAULT_BUTTON_TAG>(
     internalButtonRef,
     ref,
     useFloatingReference(),
-    isWithinPanel
-      ? null
-      : useEvent((button) => {
-          if (button) {
-            state.buttons.current.push(uniqueIdentifier)
-          } else {
-            let idx = state.buttons.current.indexOf(uniqueIdentifier)
-            if (idx !== -1) state.buttons.current.splice(idx, 1)
-          }
+    useEvent((button) => {
+      if (isWithinPanel) return
+      if (button) {
+        state.buttons.current.push(uniqueIdentifier)
+      } else {
+        let idx = state.buttons.current.indexOf(uniqueIdentifier)
+        if (idx !== -1) state.buttons.current.splice(idx, 1)
+      }
 
-          if (state.buttons.current.length > 1) {
-            console.warn(
-              'You are already using a <Popover.Button /> but only 1 <Popover.Button /> is supported.'
-            )
-          }
+      if (state.buttons.current.length > 1) {
+        console.warn(
+          'You are already using a <Popover.Button /> but only 1 <Popover.Button /> is supported.'
+        )
+      }
 
-          button && dispatch({ type: ActionTypes.SetButton, button })
-        })
+      button && dispatch({ type: ActionTypes.SetButton, button })
+    })
   )
   let withinPanelButtonRef = useSyncRefs(internalButtonRef, ref)
   let ownerDocument = useOwnerDocument(internalButtonRef)