diff --git a/packages/angular_devkit/build_angular/src/builders/karma/application_builder.ts b/packages/angular_devkit/build_angular/src/builders/karma/application_builder.ts
index 3661cfc256ef..2e6b487ab689 100644
--- a/packages/angular_devkit/build_angular/src/builders/karma/application_builder.ts
+++ b/packages/angular_devkit/build_angular/src/builders/karma/application_builder.ts
@@ -85,11 +85,19 @@ async function getProjectSourceRoot(context: BuilderContext): Promise<string> {
   return path.join(context.workspaceRoot, sourceRoot);
 }
 
+function normalizePolyfills(polyfills: string | string[] | undefined): string[] {
+  if (typeof polyfills === 'string') {
+    return [polyfills];
+  }
+
+  return polyfills ?? [];
+}
+
 async function collectEntrypoints(
   options: KarmaBuilderOptions,
   context: BuilderContext,
   projectSourceRoot: string,
-): Promise<[Set<string>, string[]]> {
+): Promise<Set<string>> {
   // Glob for files to test.
   const testFiles = await findTests(
     options.include ?? [],
@@ -102,13 +110,8 @@ async function collectEntrypoints(
     ...testFiles,
     '@angular-devkit/build-angular/src/builders/karma/init_test_bed.js',
   ]);
-  // Extract `zone.js/testing` to a separate entry point because it needs to be loaded after Jasmine.
-  const [polyfills, hasZoneTesting] = extractZoneTesting(options.polyfills);
-  if (hasZoneTesting) {
-    entryPoints.add('zone.js/testing');
-  }
 
-  return [entryPoints, polyfills];
+  return entryPoints;
 }
 
 async function initializeApplication(
@@ -129,7 +132,7 @@ async function initializeApplication(
   const testDir = path.join(context.workspaceRoot, 'dist/test-out', randomUUID());
   const projectSourceRoot = await getProjectSourceRoot(context);
 
-  const [karma, [entryPoints, polyfills]] = await Promise.all([
+  const [karma, entryPoints] = await Promise.all([
     import('karma'),
     collectEntrypoints(options, context, projectSourceRoot),
     fs.rm(testDir, { recursive: true, force: true }),
@@ -162,7 +165,7 @@ async function initializeApplication(
         },
         instrumentForCoverage,
         styles: options.styles,
-        polyfills,
+        polyfills: normalizePolyfills(options.polyfills),
         webWorkerTsConfig: options.webWorkerTsConfig,
       },
       context,
@@ -184,11 +187,10 @@ async function initializeApplication(
     // Serve polyfills first.
     { pattern: `${testDir}/polyfills.js`, type: 'module' },
     // Allow loading of chunk-* files but don't include them all on load.
-    { pattern: `${testDir}/chunk-*.js`, type: 'module', included: false },
-    // Allow loading of worker-* files but don't include them all on load.
-    { pattern: `${testDir}/worker-*.js`, type: 'module', included: false },
-    // `zone.js/testing`, served but not included on page load.
-    { pattern: `${testDir}/testing.js`, type: 'module', included: false },
+    { pattern: `${testDir}/{chunk,worker}-*.js`, type: 'module', included: false },
+  );
+
+  karmaOptions.files.push(
     // Serve remaining JS on page load, these are the test entrypoints.
     { pattern: `${testDir}/*.js`, type: 'module' },
   );
@@ -266,22 +268,6 @@ export async function writeTestFiles(files: Record<string, ResultFile>, testDir:
   });
 }
 
-function extractZoneTesting(
-  polyfills: readonly string[] | string | undefined,
-): [polyfills: string[], hasZoneTesting: boolean] {
-  if (typeof polyfills === 'string') {
-    polyfills = [polyfills];
-  }
-  polyfills ??= [];
-
-  const polyfillsWithoutZoneTesting = polyfills.filter(
-    (polyfill) => polyfill !== 'zone.js/testing',
-  );
-  const hasZoneTesting = polyfills.length !== polyfillsWithoutZoneTesting.length;
-
-  return [polyfillsWithoutZoneTesting, hasZoneTesting];
-}
-
 /** Returns the first item yielded by the given generator and cancels the execution. */
 async function first<T>(generator: AsyncIterable<T>): Promise<T> {
   for await (const value of generator) {
diff --git a/packages/angular_devkit/build_angular/src/builders/karma/tests/behavior/fake-async_spec.ts b/packages/angular_devkit/build_angular/src/builders/karma/tests/behavior/fake-async_spec.ts
new file mode 100644
index 000000000000..a6cde25eb435
--- /dev/null
+++ b/packages/angular_devkit/build_angular/src/builders/karma/tests/behavior/fake-async_spec.ts
@@ -0,0 +1,77 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
+import { execute } from '../../index';
+import { BASE_OPTIONS, KARMA_BUILDER_INFO, describeKarmaBuilder } from '../setup';
+
+describeKarmaBuilder(execute, KARMA_BUILDER_INFO, (harness, setupTarget, isApp) => {
+  describe('Behavior: "fakeAsync"', () => {
+    beforeEach(async () => {
+      await setupTarget(harness);
+    });
+
+    it('loads zone.js/testing at the right time', async () => {
+      await harness.writeFiles({
+        './src/app/app.component.ts': `
+            import { Component } from '@angular/core';
+
+            @Component({
+              selector: 'app-root',
+              template: '<button (click)="changeMessage()" class="change">{{ message }}</button>',
+            })
+            export class AppComponent {
+              message = 'Initial';
+
+              changeMessage() {
+                setTimeout(() => {
+                  this.message = 'Changed';
+                }, 1000);
+              }
+            }`,
+        './src/app/app.component.spec.ts': `
+            import { TestBed, fakeAsync, tick } from '@angular/core/testing';
+            import { By } from '@angular/platform-browser';
+            import { AppComponent } from './app.component';
+
+            describe('AppComponent', () => {
+              beforeEach(() => TestBed.configureTestingModule({
+                declarations: [AppComponent]
+              }));
+
+              it('allows terrible things that break the most basic assumptions', fakeAsync(() => {
+                const fixture = TestBed.createComponent(AppComponent);
+
+                const btn = fixture.debugElement
+                  .query(By.css('button.change'));
+
+                fixture.detectChanges();
+                expect(btn.nativeElement.innerText).toBe('Initial');
+
+                btn.triggerEventHandler('click', null);
+
+                // Pre-tick: Still the old value.
+                fixture.detectChanges();
+                expect(btn.nativeElement.innerText).toBe('Initial');
+
+                tick(1500);
+
+                fixture.detectChanges();
+                expect(btn.nativeElement.innerText).toBe('Changed');
+              }));
+            });`,
+      });
+
+      harness.useTarget('test', {
+        ...BASE_OPTIONS,
+      });
+
+      const { result } = await harness.executeOnce();
+      expect(result?.success).toBeTrue();
+    });
+  });
+});