diff --git a/src/instances.ts b/src/instances.ts
index 6be876d68..376ecd73a 100644
--- a/src/instances.ts
+++ b/src/instances.ts
@@ -375,7 +375,7 @@ export function initializeInstance(
   } else {
     if (!loader._compiler!.hooks) {
       throw new Error(
-        "You may be using an old version of webpack; please check you're using at least version 4"
+        "You may be using an old version of webpack; please check you're using at least version 4. Or you should set `transpileOnly` or `happyPackMode` to true when using with `thread-loader`."
       );
     }
 
diff --git a/src/servicesHost.ts b/src/servicesHost.ts
index 1445fd873..ff1997c1f 100644
--- a/src/servicesHost.ts
+++ b/src/servicesHost.ts
@@ -382,7 +382,6 @@ function createWatchFactory(
     }
     return result;
   }
-  ``;
 
   function invokeRecursiveDirectoryWatcher(
     directory: string,