diff --git a/src/@types/pkg.ts b/src/@types/pkg.ts
index 026eb5080..d42ba6961 100644
--- a/src/@types/pkg.ts
+++ b/src/@types/pkg.ts
@@ -20,10 +20,14 @@ export interface GithubRepo {
   head: string;
 }
 
-export interface TsType {
-  ts: 'definitely-typed' | 'included' | false;
-  definitelyTyped: string | null;
-}
+export type TsType =
+  | {
+      ts: 'included' | false | { possible: true; dtsMain: string };
+    }
+  | {
+      ts: 'definitely-typed';
+      definitelyTyped: string;
+    };
 
 export type ModuleType = 'esm' | 'cjs' | 'unknown';
 
diff --git a/src/__tests__/typescript.test.js b/src/__tests__/typescript.test.ts
similarity index 85%
rename from src/__tests__/typescript.test.js
rename to src/__tests__/typescript.test.ts
index 98f05d688..42e05f811 100644
--- a/src/__tests__/typescript.test.js
+++ b/src/__tests__/typescript.test.ts
@@ -1,5 +1,5 @@
 import * as npm from '../npm';
-import { getTypeScriptSupport } from '../typescriptSupport.js';
+import { getTypeScriptSupport } from '../typescriptSupport';
 import { fileExistsInUnpkg } from '../unpkg';
 
 jest.mock('../npm');
@@ -10,6 +10,7 @@ describe('getTypeScriptSupport()', () => {
     const typesSupport = await getTypeScriptSupport({
       name: 'Has Types',
       types: { ts: 'included' },
+      version: '1.0.0',
     });
 
     expect(typesSupport).toEqual({ types: { ts: 'included' } });
@@ -17,10 +18,12 @@ describe('getTypeScriptSupport()', () => {
 
   describe('without types/typings', () => {
     it('Checks for @types/[name]', async () => {
+      // @ts-expect-error
       npm.validatePackageExists.mockResolvedValue(true);
       const atTypesSupport = await getTypeScriptSupport({
         name: 'my-lib',
         types: { ts: false },
+        version: '1.0.0',
       });
       expect(atTypesSupport).toEqual({
         types: {
@@ -31,10 +34,12 @@ describe('getTypeScriptSupport()', () => {
     });
 
     it('Checks for @types/[scope__name]', async () => {
+      // @ts-expect-error
       npm.validatePackageExists.mockResolvedValue(true);
       const atTypesSupport = await getTypeScriptSupport({
         name: '@my-scope/my-lib',
         types: { ts: false },
+        version: '1.0.0',
       });
       expect(atTypesSupport).toEqual({
         types: {
@@ -45,23 +50,29 @@ describe('getTypeScriptSupport()', () => {
     });
 
     it('Checks for a d.ts resolved version of main', async () => {
+      // @ts-expect-error
       npm.validatePackageExists.mockResolvedValue(false);
+      // @ts-expect-error
       fileExistsInUnpkg.mockResolvedValue(true);
 
       const typesSupport = await getTypeScriptSupport({
         name: 'my-lib',
         types: { ts: { possible: true, dtsMain: 'main.d.ts' } },
+        version: '1.0.0',
       });
       expect(typesSupport).toEqual({ types: { ts: 'included' } });
     });
 
     it('Handles not having any possible TS types', async () => {
+      // @ts-expect-error
       npm.validatePackageExists.mockResolvedValue(false);
+      // @ts-expect-error
       fileExistsInUnpkg.mockResolvedValue(false);
 
       const typesSupport = await getTypeScriptSupport({
         name: 'my-lib',
         types: { ts: false },
+        version: '1.0.0',
       });
       expect(typesSupport).toEqual({ types: { ts: false } });
     });
diff --git a/src/saveDocs.js b/src/saveDocs.js
index 39008084a..4e3b6a7a0 100644
--- a/src/saveDocs.js
+++ b/src/saveDocs.js
@@ -2,7 +2,7 @@ import { getChangelogs } from './changelog';
 import formatPkg from './formatPkg.js';
 import * as jsDelivr from './jsDelivr';
 import * as npm from './npm';
-import { getTSSupport } from './typescriptSupport.js';
+import { getTSSupport } from './typescriptSupport';
 import { datadog } from './utils/datadog';
 import { log } from './utils/log';
 
diff --git a/src/typescriptSupport.js b/src/typescriptSupport.ts
similarity index 80%
rename from src/typescriptSupport.js
rename to src/typescriptSupport.ts
index f82b29db2..587b8064b 100644
--- a/src/typescriptSupport.js
+++ b/src/typescriptSupport.ts
@@ -1,3 +1,4 @@
+import type { RawPkg } from './@types/pkg';
 import * as npm from './npm';
 import { fileExistsInUnpkg } from './unpkg';
 import { datadog } from './utils/datadog';
@@ -9,7 +10,9 @@ import { datadog } from './utils/datadog';
  *   - { types: { ts: "included" }} - for types shipped with the module.
  *
  */
-export async function getTypeScriptSupport(pkg) {
+export async function getTypeScriptSupport(
+  pkg: Pick<RawPkg, 'name' | 'types' | 'version'>
+): Promise<Pick<RawPkg, 'types'>> {
   // Already calculated in `formatPkg`
   if (typeof pkg.types.ts === 'string') {
     return { types: pkg.types };
@@ -47,9 +50,11 @@ export async function getTypeScriptSupport(pkg) {
 }
 
 /**
- * @param {Array<Package>} pkgs
+ * @param pkgs
  */
-export async function getTSSupport(pkgs) {
+export async function getTSSupport(
+  pkgs: Array<Pick<RawPkg, 'name' | 'types' | 'version'>>
+): Promise<Array<Pick<RawPkg, 'types'>>> {
   const start = Date.now();
 
   const all = await Promise.all(pkgs.map(getTypeScriptSupport));