diff --git a/toolkit/components/normandy/lib/Heartbeat.jsm b/toolkit/components/normandy/lib/Heartbeat.jsm
index d5a61ca7a436..7b323365bb5f 100644
--- a/toolkit/components/normandy/lib/Heartbeat.jsm
+++ b/toolkit/components/normandy/lib/Heartbeat.jsm
@@ -4,9 +4,6 @@
 
 "use strict";
 
-const { AppConstants } = ChromeUtils.import(
-  "resource://gre/modules/AppConstants.jsm"
-);
 const { Preferences } = ChromeUtils.import(
   "resource://gre/modules/Preferences.jsm"
 );
@@ -39,10 +36,6 @@ const NOTIFICATION_TIME = 3000;
 const HEARTBEAT_CSS_URI = Services.io.newURI(
   "resource://normandy/skin/shared/Heartbeat.css"
 );
-const HEARTBEAT_CSS_URI_OSX = Services.io.newURI(
-  "resource://normandy/skin/osx/Heartbeat.css"
-);
-
 const log = LogManager.getLogger("heartbeat");
 const windowsWithInjectedCss = new WeakSet();
 let anyWindowsWithInjectedCss = false;
@@ -54,9 +47,6 @@ CleanupManager.addCleanupHandler(() => {
       if (windowsWithInjectedCss.has(window)) {
         const utils = window.windowUtils;
         utils.removeSheet(HEARTBEAT_CSS_URI, window.AGENT_SHEET);
-        if (AppConstants.platform === "macosx") {
-          utils.removeSheet(HEARTBEAT_CSS_URI_OSX, window.AGENT_SHEET);
-        }
         windowsWithInjectedCss.delete(window);
       }
     }
@@ -143,9 +133,6 @@ var Heartbeat = class {
       windowsWithInjectedCss.add(chromeWindow);
       const utils = chromeWindow.windowUtils;
       utils.loadSheet(HEARTBEAT_CSS_URI, chromeWindow.AGENT_SHEET);
-      if (AppConstants.platform === "macosx") {
-        utils.loadSheet(HEARTBEAT_CSS_URI_OSX, chromeWindow.AGENT_SHEET);
-      }
       anyWindowsWithInjectedCss = true;
     }
 
diff --git a/toolkit/components/normandy/skin/osx/Heartbeat.css b/toolkit/components/normandy/skin/osx/Heartbeat.css
deleted file mode 100644
index 936e3694d30b..000000000000
--- a/toolkit/components/normandy/skin/osx/Heartbeat.css
+++ /dev/null
@@ -1,11 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-/* Notification overrides for Heartbeat UI */
-
-notification.heartbeat {
-  background-image: linear-gradient(-179deg, #FBFBFB 0%, #EBEBEB 100%) !important;
-  border-bottom: 1px solid #C1C1C1 !important;
-  height: 40px;
-}
diff --git a/toolkit/components/normandy/skin/shared/Heartbeat.css b/toolkit/components/normandy/skin/shared/Heartbeat.css
index 5ee9a2640949..21c77bc1a50e 100644
--- a/toolkit/components/normandy/skin/shared/Heartbeat.css
+++ b/toolkit/components/normandy/skin/shared/Heartbeat.css
@@ -4,11 +4,6 @@
 
 /* Notification overrides for Heartbeat UI */
 
-notification.heartbeat {
-  border-bottom: 1px solid #C1C1C1 !important;
-  height: 40px;
-}
-
 @keyframes pulse-onshow {
   0% {
     opacity: 0;
@@ -47,16 +42,9 @@ notification.heartbeat {
   }
 }
 
-.messageText.heartbeat {
-  margin-inline-end: 12px !important; /* The !important is required to override OSX default style. */
-  margin-inline-start: 0;
-}
-
 .messageImage.heartbeat {
-  height: 24px !important;
-  margin-inline-end: 8px !important;
-  margin-inline-start: 8px !important;
-  width: 24px !important;
+  /* Needed for the animation to not get clipped when pulsing. */
+  margin-inline: 8px;
 }
 
 .messageImage.heartbeat.pulse-onshow {