--- a/browser/base/content/test/general/browser_audioTabIcon.js
+++ b/browser/base/content/test/general/browser_audioTabIcon.js
@@ -153,19 +153,20 @@ function* test_muting_using_menu(tab, ex
   // Show the popup menu
   let contextMenu = document.getElementById("tabContextMenu");
   let popupShownPromise = BrowserTestUtils.waitForEvent(contextMenu, "popupshown");
   EventUtils.synthesizeMouseAtCenter(tab, {type: "contextmenu", button: 2});
   yield popupShownPromise;
 
   // Check the menu
   let expectedLabel = expectMuted ? "Unmute Tab" : "Mute Tab";
+  let expectedAccessKey = expectMuted ? "m" : "M";
   let toggleMute = document.getElementById("context_toggleMuteTab");
   is(toggleMute.label, expectedLabel, "Correct label expected");
-  is(toggleMute.accessKey, "M", "Correct accessKey expected");
+  is(toggleMute.accessKey, expectedAccessKey, "Correct accessKey expected");
 
   is(toggleMute.hasAttribute("muted"), expectMuted, "Should have the correct state for the muted attribute");
   ok(!toggleMute.hasAttribute("soundplaying"), "Should not have the soundplaying attribute");
 
   yield play(tab);
 
   is(toggleMute.hasAttribute("muted"), expectMuted, "Should have the correct state for the muted attribute");
   ok(toggleMute.hasAttribute("soundplaying"), "Should have the soundplaying attribute");

--- a/browser/locales/en-US/chrome/browser/browser.properties
+++ b/browser/locales/en-US/chrome/browser/browser.properties
@@ -809,17 +809,17 @@ userContextNone.accesskey = N
 userContext.aboutPage.label = Manage containers
 userContext.aboutPage.accesskey = O
 
 userContextOpenLink.label = Open Link in New %S Tab
 
 muteTab.label = Mute Tab
 muteTab.accesskey = M
 unmuteTab.label = Unmute Tab
-unmuteTab.accesskey = M
+unmuteTab.accesskey = m
 playTab.label = Play Tab
 playTab.accesskey = l
 
 # LOCALIZATION NOTE (weakCryptoOverriding.message): %S is brandShortName
 weakCryptoOverriding.message = %S recommends that you don’t enter your password, credit card and other personal information on this website.
 revokeOverride.label = Don’t Trust This Website
 revokeOverride.accesskey = D