diff --git a/scripts/ci-test/karmaSafariLauncher.js b/scripts/ci-test/karmaSafariLauncher.js
index ce364790dc2..2b6eab101dc 100644
--- a/scripts/ci-test/karmaSafariLauncher.js
+++ b/scripts/ci-test/karmaSafariLauncher.js
@@ -19,7 +19,7 @@
 const fs = require('fs');
 const os = require('os');
 const path = require('path');
-const rimraf = require("rimraf");
+const rimraf = require('rimraf');
 
 var SafariBrowser = function (baseBrowserDecorator) {
   baseBrowserDecorator(this);
@@ -39,14 +39,14 @@ var SafariBrowser = function (baseBrowserDecorator) {
       path.join(SAFARI_DATA_DIR, 'Library/Caches'),
       path.join(SAFARI_DATA_DIR, 'Library/Cookies'),
       path.join(SAFARI_DATA_DIR, 'Library/Safari'),
-      path.join(SAFARI_DATA_DIR, 'Library/WebKit'),
-    ]
+      path.join(SAFARI_DATA_DIR, 'Library/WebKit')
+    ];
 
-    directoriesToClear.forEach((dir) => {
+    directoriesToClear.forEach(dir => {
       if (fs.existsSync(dir)) {
         rimraf.sync(dir);
       }
-    })
+    });
   }
 
   this._start = function (url) {
diff --git a/scripts/ci-test/test_changed.ts b/scripts/ci-test/test_changed.ts
index ed60cdc8e4a..1ea910de7d1 100644
--- a/scripts/ci-test/test_changed.ts
+++ b/scripts/ci-test/test_changed.ts
@@ -59,7 +59,12 @@ async function runTests(config: TestConfig) {
       process.exit(0);
     }
 
-    const lernaCmd = ['lerna', 'run', '--concurrency', '4'];
+    const lernaCmd = ['lerna', 'run'];
+    // Since the tests run in Safari are not headless, they share some global state when
+    // run concurrently, so we should run them serially.
+    if (process.env?.BROWSERS?.includes('Safari')) {
+      lernaCmd.push('--concurrency', '1');
+    }
     console.log(chalk`{blue Running tests in:}`);
     for (const task of testTasks) {
       if (task.reason === TestReason.Changed) {