diff --git a/spec/api-browser-window.spec.ts b/spec/api-browser-window.spec.ts
index e981bf2b3d..894eb7c465 100755
--- a/spec/api-browser-window.spec.ts
+++ b/spec/api-browser-window.spec.ts
@@ -7426,7 +7426,7 @@ describe('BrowserWindow module', () => {
       });
     });
 
-    ifdescribe(process.platform === 'darwin')('fullscreen state', () => {
+    ifdescribe(process.platform === 'darwin')('fullscreen state', { tags: ['serial'] }, () => {
       it('should not cause a crash if called when exiting fullscreen', async () => {
         const w = new BrowserWindow();
 
diff --git a/spec/chromium.spec.ts b/spec/chromium.spec.ts
index 1dff0c6f82..0b3be4bca0 100644
--- a/spec/chromium.spec.ts
+++ b/spec/chromium.spec.ts
@@ -4502,7 +4502,7 @@ describe('font fallback', () => {
   );
 });
 
-describe('iframe using HTML fullscreen API while window is OS-fullscreened', () => {
+describe('iframe using HTML fullscreen API while window is OS-fullscreened', { tags: ['serial'] }, () => {
   const fullscreenChildHtml = fs.promises.readFile(path.join(fixturesPath, 'pages', 'fullscreen-oopif.html'));
   let w: BrowserWindow;
   let server: http.Server;