diff --git a/packages/angular_devkit/build_angular/src/builders/dev-server/tests/behavior/build-assets_spec.ts b/packages/angular_devkit/build_angular/src/builders/dev-server/tests/behavior/build-assets_spec.ts
new file mode 100644
index 000000000000..48559d704967
--- /dev/null
+++ b/packages/angular_devkit/build_angular/src/builders/dev-server/tests/behavior/build-assets_spec.ts
@@ -0,0 +1,41 @@
+/**
+ * @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.io/license
+ */
+
+import { serveWebpackBrowser } from '../../index';
+import { executeOnceAndFetch } from '../execute-fetch';
+import {
+  BASE_OPTIONS,
+  DEV_SERVER_BUILDER_INFO,
+  describeBuilder,
+  setupBrowserTarget,
+} from '../setup';
+
+describeBuilder(serveWebpackBrowser, DEV_SERVER_BUILDER_INFO, (harness) => {
+  describe('Behavior: "browser builder assets"', () => {
+    it('serves a project JavaScript asset unmodified', async () => {
+      const javascriptFileContent = '/* a comment */const foo = `bar`;\n\n\n';
+      await harness.writeFile('src/extra.js', javascriptFileContent);
+
+      setupBrowserTarget(harness, {
+        assets: ['src/extra.js'],
+        optimization: {
+          scripts: true,
+        },
+      });
+
+      harness.useTarget('serve', {
+        ...BASE_OPTIONS,
+      });
+
+      const { result, response } = await executeOnceAndFetch(harness, 'extra.js');
+
+      expect(result?.success).toBeTrue();
+      expect(await response?.text()).toBe(javascriptFileContent);
+    });
+  });
+});
diff --git a/packages/angular_devkit/build_angular/src/webpack/plugins/javascript-optimizer-plugin.ts b/packages/angular_devkit/build_angular/src/webpack/plugins/javascript-optimizer-plugin.ts
index c861dd6636e1..0e7c4ba4ef59 100644
--- a/packages/angular_devkit/build_angular/src/webpack/plugins/javascript-optimizer-plugin.ts
+++ b/packages/angular_devkit/build_angular/src/webpack/plugins/javascript-optimizer-plugin.ts
@@ -96,34 +96,36 @@ export class JavaScriptOptimizerPlugin {
             }
 
             const scriptAsset = compilation.getAsset(assetName);
+            // Skip assets that have already been optimized or are verbatim copies (project assets)
+            if (!scriptAsset || scriptAsset.info.minimized || scriptAsset.info.copied) {
+              continue;
+            }
 
-            if (scriptAsset && !scriptAsset.info.minimized) {
-              const { source: scriptAssetSource, name } = scriptAsset;
-              let cacheItem;
-
-              if (cache) {
-                const eTag = cache.getLazyHashedEtag(scriptAssetSource);
-                cacheItem = cache.getItemCache(name, eTag);
-                const cachedOutput = await cacheItem.getPromise<
-                  { source: sources.Source } | undefined
-                >();
-
-                if (cachedOutput) {
-                  compilation.updateAsset(name, cachedOutput.source, {
-                    minimized: true,
-                  });
-                  continue;
-                }
+            const { source: scriptAssetSource, name } = scriptAsset;
+            let cacheItem;
+
+            if (cache) {
+              const eTag = cache.getLazyHashedEtag(scriptAssetSource);
+              cacheItem = cache.getItemCache(name, eTag);
+              const cachedOutput = await cacheItem.getPromise<
+                { source: sources.Source } | undefined
+              >();
+
+              if (cachedOutput) {
+                compilation.updateAsset(name, cachedOutput.source, {
+                  minimized: true,
+                });
+                continue;
               }
-
-              const { source, map } = scriptAssetSource.sourceAndMap();
-              scriptsToOptimize.push({
-                name: scriptAsset.name,
-                code: typeof source === 'string' ? source : source.toString(),
-                map,
-                cacheItem,
-              });
             }
+
+            const { source, map } = scriptAssetSource.sourceAndMap();
+            scriptsToOptimize.push({
+              name: scriptAsset.name,
+              code: typeof source === 'string' ? source : source.toString(),
+              map,
+              cacheItem,
+            });
           }
 
           if (scriptsToOptimize.length === 0) {