diff --git a/packages/roslib/src/core/Service.ts b/packages/roslib/src/core/Service.ts
index f8064ea0f..142857933 100644
--- a/packages/roslib/src/core/Service.ts
+++ b/packages/roslib/src/core/Service.ts
@@ -15,7 +15,10 @@ import { v4 as uuidv4 } from "uuid";
 /**
  * A ROS service client.
  */
-export default class Service<TRequest, TResponse> extends EventEmitter {
+export default class Service<
+  TRequest = unknown,
+  TResponse = unknown,
+> extends EventEmitter {
   /**
    * Stores a reference to the most recent service callback advertised so it can be removed from the EventEmitter during un-advertisement
    */
diff --git a/packages/roslib/src/core/Topic.ts b/packages/roslib/src/core/Topic.ts
index 6d3344b9f..ffc37d810 100644
--- a/packages/roslib/src/core/Topic.ts
+++ b/packages/roslib/src/core/Topic.ts
@@ -22,7 +22,7 @@ import { v4 as uuidv4 } from "uuid";
  *  * 'warning' - If there are any warning during the Topic creation.
  *  * 'message' - The message data from rosbridge.
  */
-export default class Topic<T> extends EventEmitter<{
+export default class Topic<T = unknown> extends EventEmitter<{
   message: [T];
   warning: [string];
   unsubscribe: undefined;