diff --git a/packages/@headlessui-react/src/components/dialog/dialog.tsx b/packages/@headlessui-react/src/components/dialog/dialog.tsx
index 4f3d0ed6ff..351c28ad25 100644
--- a/packages/@headlessui-react/src/components/dialog/dialog.tsx
+++ b/packages/@headlessui-react/src/components/dialog/dialog.tsx
@@ -198,14 +198,14 @@ let DialogRoot = forwardRefWithAs(function Dialog<
   useOutsideClick(
     () => {
       // Third party roots
-      let rootContainers = Array.from(ownerDocument?.querySelectorAll('body > *') ?? []).filter(
-        (container) => {
-          if (!(container instanceof HTMLElement)) return false // Skip non-HTMLElements
-          if (container.contains(mainTreeNode.current)) return false // Skip if it is the main app
-          if (state.panelRef.current && container.contains(state.panelRef.current)) return false
-          return true // Keep
-        }
-      )
+      let rootContainers = Array.from(
+        ownerDocument?.querySelectorAll('body > *, [data-headlessui-portal]') ?? []
+      ).filter((container) => {
+        if (!(container instanceof HTMLElement)) return false // Skip non-HTMLElements
+        if (container.contains(mainTreeNode.current)) return false // Skip if it is the main app
+        if (state.panelRef.current && container.contains(state.panelRef.current)) return false
+        return true // Keep
+      })
 
       return [
         ...rootContainers,
diff --git a/packages/@headlessui-react/src/components/portal/portal.test.tsx b/packages/@headlessui-react/src/components/portal/portal.test.tsx
index 6b21ea7a5c..d434dd6084 100644
--- a/packages/@headlessui-react/src/components/portal/portal.test.tsx
+++ b/packages/@headlessui-react/src/components/portal/portal.test.tsx
@@ -299,6 +299,6 @@ it('should be possible to force the Portal into a specific element using Portal.
   render(<Example />)
 
   expect(document.body.innerHTML).toMatchInlineSnapshot(
-    `"<div><main><aside id=\\"group-1\\">A<div>Next to A</div></aside><section id=\\"group-2\\"><span>B</span></section></main></div><div id=\\"headlessui-portal-root\\"><div>I am in the portal root</div></div>"`
+    `"<div><main><aside id=\\"group-1\\">A<div data-headlessui-portal=\\"\\">Next to A</div></aside><section id=\\"group-2\\"><span>B</span></section></main></div><div id=\\"headlessui-portal-root\\"><div data-headlessui-portal=\\"\\">I am in the portal root</div></div>"`
   )
 })
diff --git a/packages/@headlessui-react/src/components/portal/portal.tsx b/packages/@headlessui-react/src/components/portal/portal.tsx
index c6b55d8171..86bdba171b 100644
--- a/packages/@headlessui-react/src/components/portal/portal.tsx
+++ b/packages/@headlessui-react/src/components/portal/portal.tsx
@@ -95,6 +95,7 @@ let PortalRoot = forwardRefWithAs(function Portal<
     // Element already exists in target, always calling target.appendChild(element) will cause a
     // brief unmount/remount.
     if (!target.contains(element)) {
+      element.setAttribute('data-headlessui-portal', '')
       target.appendChild(element)
     }
 
diff --git a/packages/@headlessui-vue/src/components/dialog/dialog.ts b/packages/@headlessui-vue/src/components/dialog/dialog.ts
index 217ea2f873..dd1b24c7f3 100644
--- a/packages/@headlessui-vue/src/components/dialog/dialog.ts
+++ b/packages/@headlessui-vue/src/components/dialog/dialog.ts
@@ -179,7 +179,7 @@ export let Dialog = defineComponent({
       () => {
         // Third party roots
         let rootContainers = Array.from(
-          ownerDocument.value?.querySelectorAll('body > *') ?? []
+          ownerDocument.value?.querySelectorAll('body > *, [data-headlessui-portal]') ?? []
         ).filter((container) => {
           if (!(container instanceof HTMLElement)) return false // Skip non-HTMLElements
           if (container.contains(dom(mainTreeNode))) return false // Skip if it is the main app
diff --git a/packages/@headlessui-vue/src/components/portal/portal.test.ts b/packages/@headlessui-vue/src/components/portal/portal.test.ts
index e0baae06d0..266f3dc987 100644
--- a/packages/@headlessui-vue/src/components/portal/portal.test.ts
+++ b/packages/@headlessui-vue/src/components/portal/portal.test.ts
@@ -403,6 +403,6 @@ it('should be possible to force the Portal into a specific element using PortalG
   await new Promise<void>(nextTick)
 
   expect(document.body.innerHTML).toMatchInlineSnapshot(
-    `"<div><div><div data-v-app=\\"\\"><main><aside id=\\"group-1\\">A<div>Next to A</div></aside><section id=\\"group-2\\"><span>B</span></section><!--teleport start--><!--teleport end--></main></div></div></div>"`
+    `"<div><div><div data-v-app=\\"\\"><main><aside id=\\"group-1\\">A<div data-headlessui-portal=\\"\\">Next to A</div></aside><section id=\\"group-2\\"><span>B</span></section><!--teleport start--><!--teleport end--></main></div></div></div>"`
   )
 })
diff --git a/packages/@headlessui-vue/src/components/portal/portal.ts b/packages/@headlessui-vue/src/components/portal/portal.ts
index 3ee164d0bf..fc8e1aabe5 100644
--- a/packages/@headlessui-vue/src/components/portal/portal.ts
+++ b/packages/@headlessui-vue/src/components/portal/portal.ts
@@ -79,6 +79,7 @@ export let Portal = defineComponent({
 
       let ourProps = {
         ref: element,
+        'data-headlessui-portal': '',
       }
 
       return h(