diff --git a/e2e/specs/queue-toggle-state.spec.ts b/e2e/specs/queue-toggle-state.spec.ts
new file mode 100644
index 0000000..78ac663
--- /dev/null
+++ b/e2e/specs/queue-toggle-state.spec.ts
@@ -0,0 +1,66 @@
+import { test, expect } from '../support/fixtures.js';
+
+/**
+ * The queue button says whether the queue is open.
+ *
+ * It used to look identical in both states, so the only way to tell
+ * what pressing it would do was to look at the other side of the window
+ * and infer it — and for anyone not looking at all there was nothing to
+ * infer from: no `aria-expanded`, no `aria-controls`, no pressed state.
+ *
+ * The state is reflected *from the panel*, not kept beside the click,
+ * because the button is not the only thing that opens the queue —
+ * `now-playing-view` sets the same attribute, since it hides the bar
+ * this button lives in. A flag maintained by the click handler would be
+ * right until something else opened the panel and then quietly wrong,
+ * which is the second test here.
+ */
+test.describe('the queue toggle', () => {
+  test('reports open and closed, and names what it controls', async ({
+    app,
+  }) => {
+    const toggle = app.locator('#queue-button');
+
+    await expect(toggle).toHaveAttribute('aria-controls', 'queue-panel');
+    await expect(toggle).toHaveAttribute('aria-expanded', 'false');
+
+    await toggle.click();
+    await expect(toggle).toHaveAttribute('aria-expanded', 'true');
+
+    // The state is not only in the accessibility tree: a control that
+    // announces a state it does not draw is half a fix.
+    //
+    // Background rather than colour, because the pointer is still on
+    // the button after the click and `:hover` paints it the same accent
+    // the open state does -- so a colour comparison here passes on the
+    // broken build and proves nothing.
+    const [open, closed] = await toggle.evaluate((el) => {
+      const now = getComputedStyle(el).backgroundColor;
+
+      el.setAttribute('aria-expanded', 'false');
+      const shut = getComputedStyle(el).backgroundColor;
+
+      el.setAttribute('aria-expanded', 'true');
+
+      return [now, shut];
+    });
+
+    expect(open).not.toBe(closed);
+
+    await toggle.click();
+    await expect(toggle).toHaveAttribute('aria-expanded', 'false');
+  });
+
+  test('follows the panel when something else opens it', async ({ app }) => {
+    const toggle = app.locator('#queue-button');
+
+    await expect(toggle).toHaveAttribute('aria-expanded', 'false');
+
+    // Exactly what `now-playing-view`'s queue button does.
+    await app.evaluate(() =>
+      document.getElementById('queue-panel')?.setAttribute('open', ''),
+    );
+
+    await expect(toggle).toHaveAttribute('aria-expanded', 'true');
+  });
+});
diff --git a/frontend/index.css b/frontend/index.css
index 5d5fe0a..7549e03 100644
--- a/frontend/index.css
+++ b/frontend/index.css
@@ -207,6 +207,17 @@ body div.sidebar {
         color: var(--yj-accent, #ffd43b);
     }
 
+    /* An open queue is a state this button can be in, and it used to
+       look exactly like the closed one -- so the only way to tell what
+       pressing it would do was to look at the other side of the window
+       and infer it. `aria-expanded` is the same fact for anyone not
+       looking at all, and it points at the panel it controls. */
+    #queue-button[aria-expanded='true'] {
+        color: var(--yj-accent, #ffd43b);
+        background: var(--yj-bg-overlay, #404040);
+        border-radius: 4px;
+    }
+
     #queue-button.drag-over {
         color: var(--yj-accent, #ffd43b);
         outline: 2px dashed var(--yj-accent, #ffd43b);
diff --git a/frontend/index.html b/frontend/index.html
index 7af95aa..14b3786 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -37,7 +37,8 @@
     <footer class="bottom-bar">
         <now-playing></now-playing>
         <audio-player></audio-player>
-        <button aria-label="Toggle queue" id="queue-button">
+        <button aria-label="Toggle queue" aria-controls="queue-panel" aria-expanded="false"
+            id="queue-button">
             <wa-icon name="list"></wa-icon>
         </button>
     </footer>
diff --git a/frontend/index.ts b/frontend/index.ts
index 0b05564..2431050 100644
--- a/frontend/index.ts
+++ b/frontend/index.ts
@@ -521,6 +521,28 @@ if (queueButton && queuePanel) {
         }
     });
 
+    // The button says whether the panel is open, and it learns that
+    // from the panel rather than from its own click handler.
+    //
+    // It is not the only thing that opens the queue -- `now-playing-view`
+    // sets the same attribute, because it hides the bar this button
+    // lives in -- so a state kept beside the click would be right until
+    // something else opened the panel and then quietly wrong. The panel's
+    // `open` attribute is the one fact; this reflects it.
+    const reflectQueueState = () => {
+        queueButton.setAttribute(
+            'aria-expanded',
+            String(queuePanel.hasAttribute('open')),
+        );
+    };
+
+    new MutationObserver(reflectQueueState).observe(queuePanel, {
+        attributes: true,
+        attributeFilter: ['open'],
+    });
+
+    reflectQueueState();
+
     // ---------------------------------------------------------------
     // Queue button as drop target (when queue panel is closed)
     // ---------------------------------------------------------------