diff --git a/packages/@headlessui-react/CHANGELOG.md b/packages/@headlessui-react/CHANGELOG.md
index b4a58bfff3..07b1f16776 100644
--- a/packages/@headlessui-react/CHANGELOG.md
+++ b/packages/@headlessui-react/CHANGELOG.md
@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix prematurely added anchoring styles on `ListboxOptions` ([#3337](https://github.com/tailwindlabs/headlessui/pull/3337))
 - Ensure `unmount` on `Dialog` works in combination with the `transition` prop on `DialogBackdrop` and `DialogPanel` components ([#3352](https://github.com/tailwindlabs/headlessui/pull/3352))
 - Fix crash in `Combobox` component when in `virtual` mode when options are empty ([#3356](https://github.com/tailwindlabs/headlessui/pull/3356))
+- Fix hanging tests when using `anchor` prop ([#3357](https://github.com/tailwindlabs/headlessui/pull/3357))
 
 ## [2.1.1] - 2024-06-26
 
diff --git a/packages/@headlessui-react/src/components/popover/popover.test.tsx b/packages/@headlessui-react/src/components/popover/popover.test.tsx
index 1ca6e7d747..85d00d0f71 100644
--- a/packages/@headlessui-react/src/components/popover/popover.test.tsx
+++ b/packages/@headlessui-react/src/components/popover/popover.test.tsx
@@ -804,6 +804,26 @@ describe('Rendering', () => {
         assertActiveElement(getByText('restorable'))
       })
     )
+
+    it(
+      'should be possible to use the `anchor` prop on the `PopoverPanel`',
+      suppressConsoleLogs(async () => {
+        render(
+          <Popover>
+            <PopoverButton>Trigger</PopoverButton>
+            <PopoverPanel anchor="bottom">Panel open</PopoverPanel>
+          </Popover>
+        )
+
+        assertPopoverButton({ state: PopoverState.InvisibleUnmounted })
+        assertPopoverPanel({ state: PopoverState.InvisibleUnmounted })
+
+        await click(getPopoverButton())
+
+        assertPopoverButton({ state: PopoverState.Visible })
+        assertPopoverPanel({ state: PopoverState.Visible })
+      })
+    )
   })
 
   describe('Multiple `Popover.Button` warnings', () => {
diff --git a/packages/@headlessui-react/src/internal/floating.tsx b/packages/@headlessui-react/src/internal/floating.tsx
index 6baaa432df..216e1f9f87 100644
--- a/packages/@headlessui-react/src/internal/floating.tsx
+++ b/packages/@headlessui-react/src/internal/floating.tsx
@@ -375,9 +375,16 @@ function useFixScrollingPixel(element: HTMLElement | null) {
     if (!element) return
 
     let observer = new MutationObserver(() => {
-      let maxHeight = element.style.maxHeight
-      if (parseFloat(maxHeight) !== parseInt(maxHeight)) {
-        element.style.maxHeight = `${Math.ceil(parseFloat(maxHeight))}px`
+      let maxHeight = window.getComputedStyle(element).maxHeight
+
+      let maxHeightFloat = parseFloat(maxHeight)
+      if (isNaN(maxHeightFloat)) return
+
+      let maxHeightInt = parseInt(maxHeight)
+      if (isNaN(maxHeightInt)) return
+
+      if (maxHeightFloat !== maxHeightInt) {
+        element.style.maxHeight = `${Math.ceil(maxHeightFloat)}px`
       }
     })
 
diff --git a/playgrounds/react/pages/listbox/listbox-with-pure-tailwind.tsx b/playgrounds/react/pages/listbox/listbox-with-pure-tailwind.tsx
index 0d845b098a..de62f6945f 100644
--- a/playgrounds/react/pages/listbox/listbox-with-pure-tailwind.tsx
+++ b/playgrounds/react/pages/listbox/listbox-with-pure-tailwind.tsx
@@ -1,4 +1,4 @@
-import { Listbox, Transition } from '@headlessui/react'
+import { Label, Listbox, ListboxButton, ListboxOption, ListboxOptions } from '@headlessui/react'
 import { useEffect, useState } from 'react'
 
 let people = [
@@ -26,20 +26,12 @@ export default function Home() {
     <div className="flex h-full w-screen justify-center bg-gray-50 p-12">
       <div className="mx-auto w-full max-w-xs">
         <div className="space-y-1">
-          <Listbox
-            value={active}
-            onChange={(value) => {
-              console.log('value:', value)
-              setActivePerson(value)
-            }}
-          >
-            <Listbox.Label className="block text-sm font-medium leading-5 text-gray-700">
-              Assigned to
-            </Listbox.Label>
+          <Listbox value={active} onChange={setActivePerson}>
+            <Label className="block text-sm font-medium leading-5 text-gray-700">Assigned to</Label>
 
             <div className="relative">
               <span className="inline-block w-full rounded-md shadow-sm">
-                <Listbox.Button className="focus:shadow-outline-blue relative w-full cursor-default rounded-md border border-gray-300 bg-white py-2 pl-3 pr-10 text-left transition duration-150 ease-in-out focus:border-blue-300 focus:outline-none sm:text-sm sm:leading-5">
+                <ListboxButton className="relative w-full cursor-default rounded-md border border-gray-300 bg-white py-2 pl-3 pr-10 text-left transition duration-150 ease-in-out sm:text-sm sm:leading-5">
                   <span className="block truncate">{active}</span>
                   <span className="pointer-events-none absolute inset-y-0 right-0 flex items-center pr-2">
                     <svg
@@ -56,42 +48,35 @@ export default function Home() {
                       />
                     </svg>
                   </span>
-                </Listbox.Button>
+                </ListboxButton>
               </span>
 
-              <Transition
-                enter="transition duration-500 ease-out"
-                enterFrom="transform scale-95 opacity-0"
-                enterTo="transform scale-100 opacity-100"
-                leave="transition duration-500 ease-out"
-                leaveFrom="transform scale-100 opacity-100"
-                leaveTo="transform scale-95 opacity-0"
+              <ListboxOptions
+                anchor="bottom"
+                transition
+                className="w-[var(--button-width)] overflow-auto rounded-md border border-gray-300 bg-white py-1 text-base leading-6 shadow-lg transition duration-200 ease-out [--anchor-gap:theme(spacing.1)] [--anchor-max-height:theme(spacing.60)] focus:outline-none data-[closed]:scale-95 data-[closed]:opacity-0 sm:text-sm sm:leading-5"
               >
-                <div className="absolute mt-1 w-full rounded-md bg-white shadow-lg">
-                  <Listbox.Options className="shadow-xs max-h-60 overflow-auto rounded-md py-1 text-base leading-6 focus:outline-none sm:text-sm sm:leading-5">
-                    {people.map((name) => (
-                      <Listbox.Option
-                        key={name}
-                        value={name}
-                        className="group relative cursor-default select-none py-2 pl-3 pr-9 text-gray-900 focus:outline-none data-[active]:bg-indigo-600 data-[active]:text-white"
-                      >
-                        <span className="block truncate font-normal group-data-[selected]:font-semibold">
-                          {name}
-                        </span>
-                        <span className="absolute inset-y-0 right-0 hidden items-center pr-4 text-indigo-600 group-data-[selected]:flex group-data-[active]:text-white">
-                          <svg className="h-5 w-5" viewBox="0 0 20 20" fill="currentColor">
-                            <path
-                              fillRule="evenodd"
-                              d="M16.707 5.293a1 1 0 010 1.414l-8 8a1 1 0 01-1.414 0l-4-4a1 1 0 011.414-1.414L8 12.586l7.293-7.293a1 1 0 011.414 0z"
-                              clipRule="evenodd"
-                            />
-                          </svg>
-                        </span>
-                      </Listbox.Option>
-                    ))}
-                  </Listbox.Options>
-                </div>
-              </Transition>
+                {people.map((name) => (
+                  <ListboxOption
+                    key={name}
+                    value={name}
+                    className="group relative cursor-default select-none py-2 pl-3 pr-9 text-gray-900 focus:outline-none data-[active]:bg-indigo-600 data-[active]:text-white"
+                  >
+                    <span className="block truncate font-normal group-data-[selected]:font-semibold">
+                      {name}
+                    </span>
+                    <span className="absolute inset-y-0 right-0 hidden items-center pr-4 text-indigo-600 group-data-[selected]:flex group-data-[active]:text-white">
+                      <svg className="h-5 w-5" viewBox="0 0 20 20" fill="currentColor">
+                        <path
+                          fillRule="evenodd"
+                          d="M16.707 5.293a1 1 0 010 1.414l-8 8a1 1 0 01-1.414 0l-4-4a1 1 0 011.414-1.414L8 12.586l7.293-7.293a1 1 0 011.414 0z"
+                          clipRule="evenodd"
+                        />
+                      </svg>
+                    </span>
+                  </ListboxOption>
+                ))}
+              </ListboxOptions>
             </div>
           </Listbox>
         </div>