diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9037b50..9287b0e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,6 +13,19 @@ env:
   CI: true
 
 jobs:
+  type_checking:
+    if: "! contains(toJSON(github.event.commits.*.message), '[skip ci]')"
+    name: Check Types
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: volta-cli/action@v1
+
+      - run: yarn install --frozen-lockfile
+      - run: yarn prepack
+
+
   tests:
     if: "! contains(toJSON(github.event.commits.*.message), '[skip ci]')"
     name: Base Tests
@@ -61,7 +74,7 @@ jobs:
     name: "Compatibility"
     timeout-minutes: 7
     runs-on: ubuntu-latest
-    needs: tests
+    needs: [ tests, type_checking ]
 
     strategy:
       fail-fast: true
diff --git a/addon/index.ts b/addon/index.ts
index 290368e..c714ef1 100644
--- a/addon/index.ts
+++ b/addon/index.ts
@@ -16,7 +16,7 @@ type TransitionWithPrivateAPIs = Transition & {
   };
 };
 
-export function withHashSupport(AppRouter: typeof EmberRouter) {
+export function withHashSupport(AppRouter: typeof EmberRouter): typeof AppRouter {
   return class RouterWithHashSupport extends AppRouter {
     constructor(...args: RouterArgs) {
       super(...args);
diff --git a/tests/dummy/app/app.js b/tests/dummy/app/app.ts
similarity index 100%
rename from tests/dummy/app/app.js
rename to tests/dummy/app/app.ts
diff --git a/tests/dummy/app/router.js b/tests/dummy/app/router.ts
similarity index 100%
rename from tests/dummy/app/router.js
rename to tests/dummy/app/router.ts
diff --git a/tests/test-helper.js b/tests/test-helper.ts
similarity index 100%
rename from tests/test-helper.js
rename to tests/test-helper.ts