diff --git a/packages/schematics/angular/migrations/update-9/update-app-tsconfigs.ts b/packages/schematics/angular/migrations/update-9/update-app-tsconfigs.ts
index 99c56a37a8fd..a3bf37cb7739 100644
--- a/packages/schematics/angular/migrations/update-9/update-app-tsconfigs.ts
+++ b/packages/schematics/angular/migrations/update-9/update-app-tsconfigs.ts
@@ -7,6 +7,7 @@
  */
 import { JsonAstObject } from '@angular-devkit/core';
 import { Rule, Tree, UpdateRecorder } from '@angular-devkit/schematics';
+import { posix } from 'path';
 import {
   findPropertyInAstObject,
   insertPropertyInAstObjectInOrder,
@@ -78,29 +79,43 @@ function updateTsConfig(tree: Tree, builderConfig: JsonAstObject, builderName: B
       // Note: we need to re-read the tsconfig after very commit because
       // otherwise the updates will be out of sync since we are ammending the same node.
       tsConfigAst = readJsonFileAsAstObject(tree, tsConfigPath);
-      const files = findPropertyInAstObject(tsConfigAst, 'files');
       const include = findPropertyInAstObject(tsConfigAst, 'include');
 
-      if (!files && !include) {
-        const rootInSrc = tsConfigPath.includes('src/');
-        const rootSrc = rootInSrc ? '' : 'src/';
-        const files = builderName === Builders.Server
-          ? [`${rootSrc}main.server.ts`]
-          : [`${rootSrc}main.ts`, `${rootSrc}polyfills.ts`];
+      if (include && include.kind === 'array') {
+        const tsInclude = include.elements.find(({ value }) => typeof value === 'string' && value.endsWith('**/*.ts'));
+        if (tsInclude) {
+          const { start, end } = tsInclude;
+          recorder = tree.beginUpdate(tsConfigPath);
+          recorder.remove(start.offset, end.offset - start.offset);
+          // Replace ts includes with d.ts
+          recorder.insertLeft(start.offset, tsInclude.text.replace('.ts', '.d.ts'));
+          tree.commitUpdate(recorder);
+        }
+      }
 
-        recorder = tree.beginUpdate(tsConfigPath);
-        insertPropertyInAstObjectInOrder(recorder, tsConfigAst, 'files', files, 2);
-        tree.commitUpdate(recorder);
+      const files = findPropertyInAstObject(tsConfigAst, 'files');
+      if (!files) {
+        const newFiles: string[] = [];
 
-        if (builderName === Builders.Browser) {
-          tsConfigAst = readJsonFileAsAstObject(tree, tsConfigPath);
+        const mainOption = findPropertyInAstObject(option, 'main');
+        if (mainOption && mainOption.kind === 'string') {
+          newFiles.push(posix.relative(posix.dirname(tsConfigPath), mainOption.value));
+        }
+
+        const polyfillsOption = findPropertyInAstObject(option, 'polyfills');
+        if (polyfillsOption && polyfillsOption.kind === 'string') {
+          newFiles.push(posix.relative(posix.dirname(tsConfigPath), polyfillsOption.value));
+        }
+
+        if (newFiles.length) {
           recorder = tree.beginUpdate(tsConfigPath);
-          insertPropertyInAstObjectInOrder(recorder, tsConfigAst, 'include', [`${rootSrc}**/*.d.ts`], 2);
+          tsConfigAst = readJsonFileAsAstObject(tree, tsConfigPath);
+          insertPropertyInAstObjectInOrder(recorder, tsConfigAst, 'files', newFiles, 2);
           tree.commitUpdate(recorder);
         }
 
-        tsConfigAst = readJsonFileAsAstObject(tree, tsConfigPath);
         recorder = tree.beginUpdate(tsConfigPath);
+        tsConfigAst = readJsonFileAsAstObject(tree, tsConfigPath);
         removePropertyInAstObject(recorder, tsConfigAst, 'exclude');
         tree.commitUpdate(recorder);
       }
diff --git a/packages/schematics/angular/migrations/update-9/update-app-tsconfigs_spec.ts b/packages/schematics/angular/migrations/update-9/update-app-tsconfigs_spec.ts
index 1655d9badce6..83359f2778ca 100644
--- a/packages/schematics/angular/migrations/update-9/update-app-tsconfigs_spec.ts
+++ b/packages/schematics/angular/migrations/update-9/update-app-tsconfigs_spec.ts
@@ -58,13 +58,12 @@ describe('Migration to version 9', () => {
     it('should update apps tsConfig with stricter files inclusions', async () => {
       overrideJsonFile(tree, 'tsconfig.app.json', defaultTsConfigOptions);
       const tree2 = await schematicRunner.runSchematicAsync('migration-09', {}, tree.branch()).toPromise();
-      const { exclude, files, include } = JSON.parse(tree2.readContent('tsconfig.app.json'));
+      const { exclude, files } = JSON.parse(tree2.readContent('tsconfig.app.json'));
       expect(exclude).toBeUndefined();
       expect(files).toEqual(['src/main.ts', 'src/polyfills.ts']);
-      expect(include).toEqual(['src/**/*.d.ts']);
     });
 
-    it('should not update apps tsConfig when tsconfig has include', async () => {
+    it('should update apps tsConfig when tsconfig has include', async () => {
       const tsConfigContent = {
         ...defaultTsConfigOptions,
         include: ['foo.ts'],
@@ -74,10 +73,41 @@ describe('Migration to version 9', () => {
 
       const tree2 = await schematicRunner.runSchematicAsync('migration-09', {}, tree.branch()).toPromise();
       const { files, include } = JSON.parse(tree2.readContent('tsconfig.app.json'));
-      expect(files).toEqual(undefined);
+      expect(files).toEqual(['src/main.ts', 'src/polyfills.ts']);
       expect(include).toEqual(['foo.ts']);
     });
 
+    it(`should update include '**/*.ts' in apps tsConfig to '**/*.d.ts'`, async () => {
+      const tsConfigContent = {
+        ...defaultTsConfigOptions,
+        include: ['src/**/*.ts'],
+        exclude: ['test.ts'],
+      };
+
+      overrideJsonFile(tree, 'tsconfig.app.json', tsConfigContent);
+
+      const tree2 = await schematicRunner.runSchematicAsync('migration-09', {}, tree.branch()).toPromise();
+      const { files, include, exclude } = JSON.parse(tree2.readContent('tsconfig.app.json'));
+      expect(files).toEqual(['src/main.ts', 'src/polyfills.ts']);
+      expect(include).toEqual(['src/**/*.d.ts']);
+      expect(exclude).toBeUndefined();
+    });
+
+    it(`should update include '**/*.ts' in apps tsConfig to '**/*.d.ts' when includes contains multiple elements`, async () => {
+      const tsConfigContent = {
+        ...defaultTsConfigOptions,
+        include: ['foo.ts', 'src/**/*.ts'],
+      };
+
+      overrideJsonFile(tree, 'tsconfig.app.json', tsConfigContent);
+
+      const tree2 = await schematicRunner.runSchematicAsync('migration-09', {}, tree.branch()).toPromise();
+      const { files, include, exclude } = JSON.parse(tree2.readContent('tsconfig.app.json'));
+      expect(files).toEqual(['src/main.ts', 'src/polyfills.ts']);
+      expect(include).toEqual(['foo.ts', 'src/**/*.d.ts']);
+      expect(exclude).toBeUndefined();
+    });
+
     it(`should remove angularCompilerOptions when enableIvy is true and it's the only option`, async () => {
       overrideJsonFile(tree, 'tsconfig.app.json', defaultTsConfigOptions);
       const tree2 = await schematicRunner.runSchematicAsync('migration-09', {}, tree.branch()).toPromise();