diff --git a/packages/grpc-js/src/server.ts b/packages/grpc-js/src/server.ts
index 8d8952e8f..64c17a023 100644
--- a/packages/grpc-js/src/server.ts
+++ b/packages/grpc-js/src/server.ts
@@ -144,9 +144,13 @@ export class Server {
     throw new Error('Not implemented. Use addService() instead');
   }
 
-  addService(
-    service: ServiceDefinition,
-    implementation: UntypedServiceImplementation
+  addService<
+    ImplementationType extends {
+      [key: string]: any
+    }
+  >(
+    service: ServiceDefinition<ImplementationType>,
+    implementation: ImplementationType
   ): void {
     if (this.started === true) {
       throw new Error("Can't add a service to a started server.");
diff --git a/packages/grpc-js/test/test-server.ts b/packages/grpc-js/test/test-server.ts
index 434efbbc4..b30963fb0 100644
--- a/packages/grpc-js/test/test-server.ts
+++ b/packages/grpc-js/test/test-server.ts
@@ -181,7 +181,7 @@ describe('Server', () => {
       const server = new Server();
 
       assert.throws(() => {
-        server.addService({}, dummyImpls);
+        server.addService(({} as any), dummyImpls);
       }, /Cannot add an empty service to a server/);
     });